出名的网站有哪些,无货源电商怎么起步,手机制作游戏的app软件,建立个人网站能干C(C)数组越界但能正常运行#xff1f;关于数组越界和变量内存地址的一点研究#xff1a;何时地址连续
前言
今天美丽的本科同班同学xyy问了我一个问题#xff1a;
她出了一道C基础题#xff1a; 第一行输入一个正整数 n n n#xff08; 1 ≤ n ≤ 100 1\leq n\leq 100 …C(C)数组越界但能正常运行关于数组越界和变量内存地址的一点研究何时地址连续
前言
今天美丽的本科同班同学xyy问了我一个问题
她出了一道C基础题 第一行输入一个正整数 n n n 1 ≤ n ≤ 100 1\leq n\leq 100 1≤n≤100第二行输入空格隔开的 n n n个正整数 1 1 1到 10000 10000 10000第三行输入空格隔开的两个正整数 x x x和 y y y 1 ≤ x , y ≤ n 1\leq x, y\leq n 1≤x,y≤n按顺序输出这 n n n个数中将第 x x x个数修改为 y y y后的结果输出一行且用空格隔开 出这道题的目的之一是考察C等编程语言的数组越界问题。 n n n的最大值是 100 100 100如果开辟一个大小为 100 100 100的数组 a a a并且从下标 1 1 1开始存数据则 a [ 100 ] a[100] a[100]会发生数组越界。
测试数据中存在 n 100 n100 n100的数据题目出在了洛谷上但是对于以下代码能正常AC本题
#include bits/stdc.h
using namespace std;
int a[1];
int main() {int n;cin n;for (int i 1; i n; i) {cin a[i];}int x, y;cin x y;a[x] y;for (int i 1; i n; i) {cout a[i] ;}return 0;
}于是我就开启了对这个“越界但能正常运行”的问题进行了研究。
本地运行尝试
现在本地运行了上述代码开了个全局变量 a [ 1 ] a[1] a[1]
g xieyingying.cpp -o xieyingying.exe
./xieyingying.exe
5
1 2 3 4 5
4 100运行结果
1 2 3 100 5一切正常第 4 4 4个元素被替换成了 100 100 100其他元素没有变化。
获取元素的内存地址
将上述代码添加几行
cout a - a[100] endl;
cout n , x , y endl;获取元素在内存中的地址
#include bits/stdc.h
using namespace std;
int a[1];
int main() {int n;cin n;for (int i 1; i n; i) {cin a[i];}int x, y;cin x y;cout a - a[100] endl;cout n , x , y endl;a[x] y;for (int i 1; i n; i) {cout a[i] ;}return 0;
}运行以下命令
g xieyingying.cpp -o xieyingying.exe
./xieyingying.exe
5
1 2 3 4 5
4 100得到结果
0x407030 - 0x4071c0
0x61fe14, 0x61fe10, 0x61fe0c
1 2 3 100 5可见其实数组 a a a的地址和 n n n、 x x x、 y y y的地址并不连续。 n n n、 x x x、 y y y的地址是连续的而和 a a a相差很远。并且恰好没有其他操作使用了 a 1 a 1 a1到 a 100 a 100 a100对应的内存空间因此结果正确。
这是因为全局变量和局部变量的地址分配不在一个区中。
研究何时越界会有影响
如果我将代码修改一下将数组 a a a变成局部变量
#include bits/stdc.h
using namespace std;
int main() {int a[1];int n;cin n;for (int i 1; i n; i) {cin a[i];}int x, y;cin x y;cout a - a[100] endl;cout n , x , y endl;a[x] y;for (int i 1; i n; i) {cout a[i] ;}return 0;
}运行以下命令
g xieyingying2.cpp -o xieyingying2.exe
./xieyingying2.exe
5
1 2 3 4 5
4 100得到结果
0x61fe14 - 0x61ffa4
0x61fe10, 0x61fe0c, 0x61fe08
1 6 3 100 5嘿嘿内存空间一连续答案不对了吧。
其实第一版代码如果后续操作过多“数组中”元素也会有概率被修改的。
但是你看我是一个出题者出了一道题在洛谷上我没办法修改编译选项如开启ASAN也没办法限制用户不许将数组开到全局变量而其他元素开到局部变量。那么怎么办才好呢
一个比较可行的让不注意选手 答案错误 的方式
我能想到的办法只有修改题目了。毕竟主要是在考“数组越界”因此可以将题目修改为 第一行输入一个正整数 n n n 1 ≤ n ≤ 100 1\leq n\leq 100 1≤n≤100第二行输入空格隔开的 n n n个正整数 1 1 1到 10000 10000 10000代表数组 a a a中的元素第三行输入空格隔开的 n n n个正整数 1 1 1到 10000 10000 10000代表数组 b b b中的元素第四行输入空格隔开的两个正整数 x x x和 y y y 1 ≤ x , y ≤ n 1\leq x, y\leq n 1≤x,y≤n交换 a [ x ] a[x] a[x]和 b [ y ] b[y] b[y]并按顺序输出数组 a a a和数组 b b b中的元素每个输出一行且用不用元素之间用空格隔开 也就是说现在有两个数组 a a a和 b b b一般人不会把这两个数组一个开到全局一个开到局部吧。假设这两个数组开到了一个位置那么不管是全局还是局部都会冲突。
为了易读性假设 n n n的范围是 1 1 1到 5 5 5对于以下代码
#include bits/stdc.h
using namespace std;
int a[5];
int b[5];
int main() {cout a - a[5] endl;cout b - b[5] endl;int n;cin n;for (int i 1; i n; i) {cin a[i];}for (int i 1; i n; i) {cin b[i];}int x, y;cin x y;swap(a[x], b[y]);for (int i 1; i n; i) {cout a[i] ;}for (int i 1; i n; i) {cout b[i] ;}return 0;
}运行以下命令
g xieyingying.cpp -o xieyingying.exe
./xieyingying.exe
5
1 2 3 4 5
100 200 300 400 500
2 4运行结果
0x407030 - 0x407044
0x407050 - 0x407064
1 400 3 4 5 100 200 300 2 500 纳尼结果仍然正确虽然数组 a a a后立刻开辟了数组 b b b并且它们的大小都为 5 5 5但是 a [ 5 ] a[5] a[5]地址仍不等于 b b b的地址
何时内存地址连续
尝试使用以下代码来获取数组在内存中的地址
#include bits/stdc.h
using namespace std;#define SIZE 100
int a[SIZE], b[SIZE];
int main() {cout a - a[SIZE] endl;cout b - b[SIZE] endl;return 0;
}执行以下命令
g xieyingying4.cpp -o xieyingying4.exe
./xieyingying4.exe得到结果
0x407040 - 0x4071d0
0x4071e0 - 0x407370可见0x4071d0不等于0x4071e0内存仍不连续。
接下来将SIZE修改为1、2、…发现有时候数组地址是连续的有时候是不连续的。
写个脚本判断数组大小为1到128时何时连续
import osfor i in range(1, 128 1):source
#include bits/stdc.h
using namespace std;
typedef long long ll;#define SIZE str(i)
int a[SIZE], b[SIZE];
int main() {cout a - a[SIZE] | ;cout b - b[SIZE] | ;cout ((ll)a[SIZE] (ll)b);return 0;
}
with open(source.cpp, w, encodingutf-8) as f:f.write(source)os.system(g source.cpp -o source.exe)exe os.popen(source.exe)result exe.read()ifSame result[-1] 1print(fi {i}({same if ifSame else different}): {result})执行后可以得到结果
i 1(same): 0x407030 - 0x407034 | 0x407034 - 0x407038 | 1
i 2(same): 0x407030 - 0x407038 | 0x407038 - 0x407040 | 1
i 3(different): 0x407030 - 0x40703c | 0x407040 - 0x40704c | 0
i 4(same): 0x407030 - 0x407040 | 0x407040 - 0x407050 | 1
i 5(different): 0x407030 - 0x407044 | 0x407050 - 0x407064 | 0
i 6(different): 0x407030 - 0x407048 | 0x407050 - 0x407068 | 0
i 8(same): 0x407040 - 0x407060 | 0x407060 - 0x407080 | 1
i 9(different): 0x407040 - 0x407064 | 0x407080 - 0x4070a4 | 0
i 10(different): 0x407040 - 0x407068 | 0x407080 - 0x4070a8 | 0
i 11(different): 0x407040 - 0x40706c | 0x407080 - 0x4070ac | 0
i 12(different): 0x407040 - 0x407070 | 0x407080 - 0x4070b0 | 0
i 13(different): 0x407040 - 0x407074 | 0x407080 - 0x4070b4 | 0
i 14(different): 0x407040 - 0x407078 | 0x407080 - 0x4070b8 | 0
i 15(different): 0x407040 - 0x40707c | 0x407080 - 0x4070bc | 0
i 16(same): 0x407040 - 0x407080 | 0x407080 - 0x4070c0 | 1
i 17(different): 0x407040 - 0x407084 | 0x4070a0 - 0x4070e4 | 0
i 18(different): 0x407040 - 0x407088 | 0x4070a0 - 0x4070e8 | 0
i 19(different): 0x407040 - 0x40708c | 0x4070a0 - 0x4070ec | 0
i 20(different): 0x407040 - 0x407090 | 0x4070a0 - 0x4070f0 | 0
i 21(different): 0x407040 - 0x407094 | 0x4070a0 - 0x4070f4 | 0
i 22(different): 0x407040 - 0x407098 | 0x4070a0 - 0x4070f8 | 0
i 23(different): 0x407040 - 0x40709c | 0x4070a0 - 0x4070fc | 0
i 24(same): 0x407040 - 0x4070a0 | 0x4070a0 - 0x407100 | 1
i 25(different): 0x407040 - 0x4070a4 | 0x4070c0 - 0x407124 | 0
i 26(different): 0x407040 - 0x4070a8 | 0x4070c0 - 0x407128 | 0
i 27(different): 0x407040 - 0x4070ac | 0x4070c0 - 0x40712c | 0
i 28(different): 0x407040 - 0x4070b0 | 0x4070c0 - 0x407130 | 0
i 29(different): 0x407040 - 0x4070b4 | 0x4070c0 - 0x407134 | 0
i 30(different): 0x407040 - 0x4070b8 | 0x4070c0 - 0x407138 | 0
i 31(different): 0x407040 - 0x4070bc | 0x4070c0 - 0x40713c | 0
i 32(same): 0x407040 - 0x4070c0 | 0x4070c0 - 0x407140 | 1
i 33(different): 0x407040 - 0x4070c4 | 0x4070e0 - 0x407164 | 0
i 34(different): 0x407040 - 0x4070c8 | 0x4070e0 - 0x407168 | 0
i 35(different): 0x407040 - 0x4070cc | 0x4070e0 - 0x40716c | 0
i 36(different): 0x407040 - 0x4070d0 | 0x4070e0 - 0x407170 | 0
i 37(different): 0x407040 - 0x4070d4 | 0x4070e0 - 0x407174 | 0
i 38(different): 0x407040 - 0x4070d8 | 0x4070e0 - 0x407178 | 0
i 39(different): 0x407040 - 0x4070dc | 0x4070e0 - 0x40717c | 0
i 40(same): 0x407040 - 0x4070e0 | 0x4070e0 - 0x407180 | 1
i 41(different): 0x407040 - 0x4070e4 | 0x407100 - 0x4071a4 | 0
i 42(different): 0x407040 - 0x4070e8 | 0x407100 - 0x4071a8 | 0
i 43(different): 0x407040 - 0x4070ec | 0x407100 - 0x4071ac | 0
i 44(different): 0x407040 - 0x4070f0 | 0x407100 - 0x4071b0 | 0
i 45(different): 0x407040 - 0x4070f4 | 0x407100 - 0x4071b4 | 0
i 46(different): 0x407040 - 0x4070f8 | 0x407100 - 0x4071b8 | 0
i 47(different): 0x407040 - 0x4070fc | 0x407100 - 0x4071bc | 0
i 48(same): 0x407040 - 0x407100 | 0x407100 - 0x4071c0 | 1
i 49(different): 0x407040 - 0x407104 | 0x407120 - 0x4071e4 | 0
i 50(different): 0x407040 - 0x407108 | 0x407120 - 0x4071e8 | 0
i 51(different): 0x407040 - 0x40710c | 0x407120 - 0x4071ec | 0
i 52(different): 0x407040 - 0x407110 | 0x407120 - 0x4071f0 | 0
i 53(different): 0x407040 - 0x407114 | 0x407120 - 0x4071f4 | 0
i 54(different): 0x407040 - 0x407118 | 0x407120 - 0x4071f8 | 0
i 55(different): 0x407040 - 0x40711c | 0x407120 - 0x4071fc | 0
i 56(same): 0x407040 - 0x407120 | 0x407120 - 0x407200 | 1
i 57(different): 0x407040 - 0x407124 | 0x407140 - 0x407224 | 0
i 58(different): 0x407040 - 0x407128 | 0x407140 - 0x407228 | 0
i 59(different): 0x407040 - 0x40712c | 0x407140 - 0x40722c | 0
i 60(different): 0x407040 - 0x407130 | 0x407140 - 0x407230 | 0
i 61(different): 0x407040 - 0x407134 | 0x407140 - 0x407234 | 0
i 62(different): 0x407040 - 0x407138 | 0x407140 - 0x407238 | 0
i 63(different): 0x407040 - 0x40713c | 0x407140 - 0x40723c | 0
i 64(same): 0x407040 - 0x407140 | 0x407140 - 0x407240 | 1
i 65(different): 0x407040 - 0x407144 | 0x407160 - 0x407264 | 0
i 66(different): 0x407040 - 0x407148 | 0x407160 - 0x407268 | 0
i 67(different): 0x407040 - 0x40714c | 0x407160 - 0x40726c | 0
i 68(different): 0x407040 - 0x407150 | 0x407160 - 0x407270 | 0
i 69(different): 0x407040 - 0x407154 | 0x407160 - 0x407274 | 0
i 70(different): 0x407040 - 0x407158 | 0x407160 - 0x407278 | 0
i 71(different): 0x407040 - 0x40715c | 0x407160 - 0x40727c | 0
i 72(same): 0x407040 - 0x407160 | 0x407160 - 0x407280 | 1
i 73(different): 0x407040 - 0x407164 | 0x407180 - 0x4072a4 | 0
i 74(different): 0x407040 - 0x407168 | 0x407180 - 0x4072a8 | 0
i 75(different): 0x407040 - 0x40716c | 0x407180 - 0x4072ac | 0
i 76(different): 0x407040 - 0x407170 | 0x407180 - 0x4072b0 | 0
i 77(different): 0x407040 - 0x407174 | 0x407180 - 0x4072b4 | 0
i 78(different): 0x407040 - 0x407178 | 0x407180 - 0x4072b8 | 0
i 79(different): 0x407040 - 0x40717c | 0x407180 - 0x4072bc | 0
i 80(same): 0x407040 - 0x407180 | 0x407180 - 0x4072c0 | 1
i 81(different): 0x407040 - 0x407184 | 0x4071a0 - 0x4072e4 | 0
i 82(different): 0x407040 - 0x407188 | 0x4071a0 - 0x4072e8 | 0
i 83(different): 0x407040 - 0x40718c | 0x4071a0 - 0x4072ec | 0
i 84(different): 0x407040 - 0x407190 | 0x4071a0 - 0x4072f0 | 0
i 85(different): 0x407040 - 0x407194 | 0x4071a0 - 0x4072f4 | 0
i 86(different): 0x407040 - 0x407198 | 0x4071a0 - 0x4072f8 | 0
i 87(different): 0x407040 - 0x40719c | 0x4071a0 - 0x4072fc | 0
i 88(same): 0x407040 - 0x4071a0 | 0x4071a0 - 0x407300 | 1
i 89(different): 0x407040 - 0x4071a4 | 0x4071c0 - 0x407324 | 0
i 90(different): 0x407040 - 0x4071a8 | 0x4071c0 - 0x407328 | 0
i 91(different): 0x407040 - 0x4071ac | 0x4071c0 - 0x40732c | 0
i 92(different): 0x407040 - 0x4071b0 | 0x4071c0 - 0x407330 | 0
i 93(different): 0x407040 - 0x4071b4 | 0x4071c0 - 0x407334 | 0
i 94(different): 0x407040 - 0x4071b8 | 0x4071c0 - 0x407338 | 0
i 95(different): 0x407040 - 0x4071bc | 0x4071c0 - 0x40733c | 0
i 96(same): 0x407040 - 0x4071c0 | 0x4071c0 - 0x407340 | 1
i 97(different): 0x407040 - 0x4071c4 | 0x4071e0 - 0x407364 | 0
i 98(different): 0x407040 - 0x4071c8 | 0x4071e0 - 0x407368 | 0
i 99(different): 0x407040 - 0x4071cc | 0x4071e0 - 0x40736c | 0
i 100(different): 0x407040 - 0x4071d0 | 0x4071e0 - 0x407370 | 0
i 101(different): 0x407040 - 0x4071d4 | 0x4071e0 - 0x407374 | 0
i 102(different): 0x407040 - 0x4071d8 | 0x4071e0 - 0x407378 | 0
i 103(different): 0x407040 - 0x4071dc | 0x4071e0 - 0x40737c | 0
i 104(same): 0x407040 - 0x4071e0 | 0x4071e0 - 0x407380 | 1
i 105(different): 0x407040 - 0x4071e4 | 0x407200 - 0x4073a4 | 0
i 106(different): 0x407040 - 0x4071e8 | 0x407200 - 0x4073a8 | 0
i 107(different): 0x407040 - 0x4071ec | 0x407200 - 0x4073ac | 0
i 108(different): 0x407040 - 0x4071f0 | 0x407200 - 0x4073b0 | 0
i 109(different): 0x407040 - 0x4071f4 | 0x407200 - 0x4073b4 | 0
i 110(different): 0x407040 - 0x4071f8 | 0x407200 - 0x4073b8 | 0
i 111(different): 0x407040 - 0x4071fc | 0x407200 - 0x4073bc | 0
i 112(same): 0x407040 - 0x407200 | 0x407200 - 0x4073c0 | 1
i 113(different): 0x407040 - 0x407204 | 0x407220 - 0x4073e4 | 0
i 114(different): 0x407040 - 0x407208 | 0x407220 - 0x4073e8 | 0
i 115(different): 0x407040 - 0x40720c | 0x407220 - 0x4073ec | 0
i 116(different): 0x407040 - 0x407210 | 0x407220 - 0x4073f0 | 0
i 117(different): 0x407040 - 0x407214 | 0x407220 - 0x4073f4 | 0
i 118(different): 0x407040 - 0x407218 | 0x407220 - 0x4073f8 | 0
i 119(different): 0x407040 - 0x40721c | 0x407220 - 0x4073fc | 0
i 120(same): 0x407040 - 0x407220 | 0x407220 - 0x407400 | 1
i 121(different): 0x407040 - 0x407224 | 0x407240 - 0x407424 | 0
i 122(different): 0x407040 - 0x407228 | 0x407240 - 0x407428 | 0
i 123(different): 0x407040 - 0x40722c | 0x407240 - 0x40742c | 0
i 124(different): 0x407040 - 0x407230 | 0x407240 - 0x407430 | 0
i 125(different): 0x407040 - 0x407234 | 0x407240 - 0x407434 | 0
i 126(different): 0x407040 - 0x407238 | 0x407240 - 0x407438 | 0
i 127(different): 0x407040 - 0x40723c | 0x407240 - 0x40743c | 0
i 128(same): 0x407040 - 0x407240 | 0x407240 - 0x407440 | 1可以发现
在全局变量中连续开辟两个大小相同的数组当数组大小SIZE满足以下条件时两个数组的内存地址连续 { S I Z E ∈ { 1 , 2 , 4 } if S I Z E 8 S I Z E ∈ { 8 k ∣ k 为整数 } if 8 ≤ S I Z E ≤ 128 \begin{cases} SIZE\in\{1,2,4\} \text{ if } SIZE8 \\ SIZE\in\{8k|k为整数\} \text{ if } 8\leq SIZE\leq 128 \end{cases} {SIZE∈{1,2,4} if SIZE8SIZE∈{8k∣k为整数} if 8≤SIZE≤128
换一台机器同为Win10的执行结果也是一样的。
但是当我把数组 a a a和数组 b b b开到局部变量时啊咧全部不一样。。。
i 1(different): 0x61fe1c - 0x61fe20 | 0x61fe18 - 0x61fe1c | 0
i 2(different): 0x61fe18 - 0x61fe20 | 0x61fe10 - 0x61fe18 | 0
i 3(different): 0x61fe14 - 0x61fe20 | 0x61fe08 - 0x61fe14 | 0
i 4(different): 0x61fe10 - 0x61fe20 | 0x61fe00 - 0x61fe10 | 0
i 5(different): 0x61fe00 - 0x61fe14 | 0x61fde0 - 0x61fdf4 | 0
i 6(different): 0x61fe00 - 0x61fe18 | 0x61fde0 - 0x61fdf8 | 0
i 7(different): 0x61fe00 - 0x61fe1c | 0x61fde0 - 0x61fdfc | 0
i 8(different): 0x61fe00 - 0x61fe20 | 0x61fde0 - 0x61fe00 | 0
i 9(different): 0x61fdf0 - 0x61fe14 | 0x61fdc0 - 0x61fde4 | 0
i 10(different): 0x61fdf0 - 0x61fe18 | 0x61fdc0 - 0x61fde8 | 0
i 11(different): 0x61fdf0 - 0x61fe1c | 0x61fdc0 - 0x61fdec | 0
i 12(different): 0x61fdf0 - 0x61fe20 | 0x61fdc0 - 0x61fdf0 | 0
i 13(different): 0x61fde0 - 0x61fe14 | 0x61fda0 - 0x61fdd4 | 0
i 14(different): 0x61fde0 - 0x61fe18 | 0x61fda0 - 0x61fdd8 | 0
i 15(different): 0x61fde0 - 0x61fe1c | 0x61fda0 - 0x61fddc | 0
i 16(different): 0x61fde0 - 0x61fe20 | 0x61fda0 - 0x61fde0 | 0
i 17(different): 0x61fdd0 - 0x61fe14 | 0x61fd80 - 0x61fdc4 | 0
i 18(different): 0x61fdd0 - 0x61fe18 | 0x61fd80 - 0x61fdc8 | 0
i 19(different): 0x61fdd0 - 0x61fe1c | 0x61fd80 - 0x61fdcc | 0
i 20(different): 0x61fdd0 - 0x61fe20 | 0x61fd80 - 0x61fdd0 | 0
i 21(different): 0x61fdc0 - 0x61fe14 | 0x61fd60 - 0x61fdb4 | 0
i 22(different): 0x61fdc0 - 0x61fe18 | 0x61fd60 - 0x61fdb8 | 0
i 23(different): 0x61fdc0 - 0x61fe1c | 0x61fd60 - 0x61fdbc | 0
i 24(different): 0x61fdc0 - 0x61fe20 | 0x61fd60 - 0x61fdc0 | 0
i 25(different): 0x61fdb0 - 0x61fe14 | 0x61fd40 - 0x61fda4 | 0
i 26(different): 0x61fdb0 - 0x61fe18 | 0x61fd40 - 0x61fda8 | 0
i 27(different): 0x61fdb0 - 0x61fe1c | 0x61fd40 - 0x61fdac | 0
i 28(different): 0x61fdb0 - 0x61fe20 | 0x61fd40 - 0x61fdb0 | 0
i 29(different): 0x61fda0 - 0x61fe14 | 0x61fd20 - 0x61fd94 | 0
i 30(different): 0x61fda0 - 0x61fe18 | 0x61fd20 - 0x61fd98 | 0
i 31(different): 0x61fda0 - 0x61fe1c | 0x61fd20 - 0x61fd9c | 0
i 32(different): 0x61fda0 - 0x61fe20 | 0x61fd20 - 0x61fda0 | 0
i 33(different): 0x61fd90 - 0x61fe14 | 0x61fd00 - 0x61fd84 | 0
i 34(different): 0x61fd90 - 0x61fe18 | 0x61fd00 - 0x61fd88 | 0
i 35(different): 0x61fd90 - 0x61fe1c | 0x61fd00 - 0x61fd8c | 0
i 36(different): 0x61fd90 - 0x61fe20 | 0x61fd00 - 0x61fd90 | 0
i 37(different): 0x61fd80 - 0x61fe14 | 0x61fce0 - 0x61fd74 | 0
i 38(different): 0x61fd80 - 0x61fe18 | 0x61fce0 - 0x61fd78 | 0
i 39(different): 0x61fd80 - 0x61fe1c | 0x61fce0 - 0x61fd7c | 0
i 40(different): 0x61fd80 - 0x61fe20 | 0x61fce0 - 0x61fd80 | 0
i 41(different): 0x61fd70 - 0x61fe14 | 0x61fcc0 - 0x61fd64 | 0
i 42(different): 0x61fd70 - 0x61fe18 | 0x61fcc0 - 0x61fd68 | 0
i 43(different): 0x61fd70 - 0x61fe1c | 0x61fcc0 - 0x61fd6c | 0
i 44(different): 0x61fd70 - 0x61fe20 | 0x61fcc0 - 0x61fd70 | 0
i 45(different): 0x61fd60 - 0x61fe14 | 0x61fca0 - 0x61fd54 | 0
i 46(different): 0x61fd60 - 0x61fe18 | 0x61fca0 - 0x61fd58 | 0
i 47(different): 0x61fd60 - 0x61fe1c | 0x61fca0 - 0x61fd5c | 0
i 48(different): 0x61fd60 - 0x61fe20 | 0x61fca0 - 0x61fd60 | 0
i 49(different): 0x61fd50 - 0x61fe14 | 0x61fc80 - 0x61fd44 | 0
i 50(different): 0x61fd50 - 0x61fe18 | 0x61fc80 - 0x61fd48 | 0
i 51(different): 0x61fd50 - 0x61fe1c | 0x61fc80 - 0x61fd4c | 0
i 52(different): 0x61fd50 - 0x61fe20 | 0x61fc80 - 0x61fd50 | 0
i 53(different): 0x61fd40 - 0x61fe14 | 0x61fc60 - 0x61fd34 | 0
i 54(different): 0x61fd40 - 0x61fe18 | 0x61fc60 - 0x61fd38 | 0
i 55(different): 0x61fd40 - 0x61fe1c | 0x61fc60 - 0x61fd3c | 0
i 56(different): 0x61fd40 - 0x61fe20 | 0x61fc60 - 0x61fd40 | 0
i 57(different): 0x61fd30 - 0x61fe14 | 0x61fc40 - 0x61fd24 | 0
i 58(different): 0x61fd30 - 0x61fe18 | 0x61fc40 - 0x61fd28 | 0
i 59(different): 0x61fd30 - 0x61fe1c | 0x61fc40 - 0x61fd2c | 0
i 60(different): 0x61fd30 - 0x61fe20 | 0x61fc40 - 0x61fd30 | 0
i 61(different): 0x61fd20 - 0x61fe14 | 0x61fc20 - 0x61fd14 | 0
i 62(different): 0x61fd20 - 0x61fe18 | 0x61fc20 - 0x61fd18 | 0
i 63(different): 0x61fd20 - 0x61fe1c | 0x61fc20 - 0x61fd1c | 0
i 64(different): 0x61fd20 - 0x61fe20 | 0x61fc20 - 0x61fd20 | 0
i 65(different): 0x61fd10 - 0x61fe14 | 0x61fc00 - 0x61fd04 | 0
i 66(different): 0x61fd10 - 0x61fe18 | 0x61fc00 - 0x61fd08 | 0
i 67(different): 0x61fd10 - 0x61fe1c | 0x61fc00 - 0x61fd0c | 0
i 68(different): 0x61fd10 - 0x61fe20 | 0x61fc00 - 0x61fd10 | 0
i 69(different): 0x61fd00 - 0x61fe14 | 0x61fbe0 - 0x61fcf4 | 0
i 70(different): 0x61fd00 - 0x61fe18 | 0x61fbe0 - 0x61fcf8 | 0
i 71(different): 0x61fd00 - 0x61fe1c | 0x61fbe0 - 0x61fcfc | 0
i 72(different): 0x61fd00 - 0x61fe20 | 0x61fbe0 - 0x61fd00 | 0
i 73(different): 0x61fcf0 - 0x61fe14 | 0x61fbc0 - 0x61fce4 | 0
i 74(different): 0x61fcf0 - 0x61fe18 | 0x61fbc0 - 0x61fce8 | 0
i 75(different): 0x61fcf0 - 0x61fe1c | 0x61fbc0 - 0x61fcec | 0
i 76(different): 0x61fcf0 - 0x61fe20 | 0x61fbc0 - 0x61fcf0 | 0
i 77(different): 0x61fce0 - 0x61fe14 | 0x61fba0 - 0x61fcd4 | 0
i 78(different): 0x61fce0 - 0x61fe18 | 0x61fba0 - 0x61fcd8 | 0
i 79(different): 0x61fce0 - 0x61fe1c | 0x61fba0 - 0x61fcdc | 0
i 80(different): 0x61fce0 - 0x61fe20 | 0x61fba0 - 0x61fce0 | 0
i 81(different): 0x61fcd0 - 0x61fe14 | 0x61fb80 - 0x61fcc4 | 0
i 82(different): 0x61fcd0 - 0x61fe18 | 0x61fb80 - 0x61fcc8 | 0
i 83(different): 0x61fcd0 - 0x61fe1c | 0x61fb80 - 0x61fccc | 0
i 84(different): 0x61fcd0 - 0x61fe20 | 0x61fb80 - 0x61fcd0 | 0
i 85(different): 0x61fcc0 - 0x61fe14 | 0x61fb60 - 0x61fcb4 | 0
i 86(different): 0x61fcc0 - 0x61fe18 | 0x61fb60 - 0x61fcb8 | 0
i 87(different): 0x61fcc0 - 0x61fe1c | 0x61fb60 - 0x61fcbc | 0
i 88(different): 0x61fcc0 - 0x61fe20 | 0x61fb60 - 0x61fcc0 | 0
i 89(different): 0x61fcb0 - 0x61fe14 | 0x61fb40 - 0x61fca4 | 0
i 90(different): 0x61fcb0 - 0x61fe18 | 0x61fb40 - 0x61fca8 | 0
i 91(different): 0x61fcb0 - 0x61fe1c | 0x61fb40 - 0x61fcac | 0
i 92(different): 0x61fcb0 - 0x61fe20 | 0x61fb40 - 0x61fcb0 | 0
i 93(different): 0x61fca0 - 0x61fe14 | 0x61fb20 - 0x61fc94 | 0
i 94(different): 0x61fca0 - 0x61fe18 | 0x61fb20 - 0x61fc98 | 0
i 95(different): 0x61fca0 - 0x61fe1c | 0x61fb20 - 0x61fc9c | 0
i 96(different): 0x61fca0 - 0x61fe20 | 0x61fb20 - 0x61fca0 | 0
i 97(different): 0x61fc90 - 0x61fe14 | 0x61fb00 - 0x61fc84 | 0
i 98(different): 0x61fc90 - 0x61fe18 | 0x61fb00 - 0x61fc88 | 0
i 99(different): 0x61fc90 - 0x61fe1c | 0x61fb00 - 0x61fc8c | 0
i 100(different): 0x61fc90 - 0x61fe20 | 0x61fb00 - 0x61fc90 | 0
i 101(different): 0x61fc80 - 0x61fe14 | 0x61fae0 - 0x61fc74 | 0
i 102(different): 0x61fc80 - 0x61fe18 | 0x61fae0 - 0x61fc78 | 0
i 103(different): 0x61fc80 - 0x61fe1c | 0x61fae0 - 0x61fc7c | 0
i 104(different): 0x61fc80 - 0x61fe20 | 0x61fae0 - 0x61fc80 | 0
i 105(different): 0x61fc70 - 0x61fe14 | 0x61fac0 - 0x61fc64 | 0
i 106(different): 0x61fc70 - 0x61fe18 | 0x61fac0 - 0x61fc68 | 0
i 107(different): 0x61fc70 - 0x61fe1c | 0x61fac0 - 0x61fc6c | 0
i 108(different): 0x61fc70 - 0x61fe20 | 0x61fac0 - 0x61fc70 | 0
i 109(different): 0x61fc60 - 0x61fe14 | 0x61faa0 - 0x61fc54 | 0
i 110(different): 0x61fc60 - 0x61fe18 | 0x61faa0 - 0x61fc58 | 0
i 111(different): 0x61fc60 - 0x61fe1c | 0x61faa0 - 0x61fc5c | 0
i 112(different): 0x61fc60 - 0x61fe20 | 0x61faa0 - 0x61fc60 | 0
i 113(different): 0x61fc50 - 0x61fe14 | 0x61fa80 - 0x61fc44 | 0
i 114(different): 0x61fc50 - 0x61fe18 | 0x61fa80 - 0x61fc48 | 0
i 115(different): 0x61fc50 - 0x61fe1c | 0x61fa80 - 0x61fc4c | 0
i 116(different): 0x61fc50 - 0x61fe20 | 0x61fa80 - 0x61fc50 | 0
i 117(different): 0x61fc40 - 0x61fe14 | 0x61fa60 - 0x61fc34 | 0
i 118(different): 0x61fc40 - 0x61fe18 | 0x61fa60 - 0x61fc38 | 0
i 119(different): 0x61fc40 - 0x61fe1c | 0x61fa60 - 0x61fc3c | 0
i 120(different): 0x61fc40 - 0x61fe20 | 0x61fa60 - 0x61fc40 | 0
i 121(different): 0x61fc30 - 0x61fe14 | 0x61fa40 - 0x61fc24 | 0
i 122(different): 0x61fc30 - 0x61fe18 | 0x61fa40 - 0x61fc28 | 0
i 123(different): 0x61fc30 - 0x61fe1c | 0x61fa40 - 0x61fc2c | 0
i 124(different): 0x61fc30 - 0x61fe20 | 0x61fa40 - 0x61fc30 | 0
i 125(different): 0x61fc20 - 0x61fe14 | 0x61fa20 - 0x61fc14 | 0
i 126(different): 0x61fc20 - 0x61fe18 | 0x61fa20 - 0x61fc18 | 0
i 127(different): 0x61fc20 - 0x61fe1c | 0x61fa20 - 0x61fc1c | 0
i 128(different): 0x61fc20 - 0x61fe20 | 0x61fa20 - 0x61fc20 | 0正当我沮丧之时忽然发现数组 b b b的起始地址小于数组 a a a的“越界地址”因此是会产生“数据覆盖”的。
何时真正可以 第一行输入一个正整数 n n n 1 ≤ n ≤ 128 1\leq n\leq 128 1≤n≤128第二行输入空格隔开的 n n n个正整数 1 1 1到 10000 10000 10000代表数组 a a a中的元素第三行输入空格隔开的 n n n个正整数 1 1 1到 10000 10000 10000代表数组 b b b中的元素第四行输入空格隔开的两个正整数 x x x和 y y y 1 ≤ x , y ≤ n 1\leq x, y\leq n 1≤x,y≤n交换 a [ x ] a[x] a[x]和 b [ y ] b[y] b[y]并按顺序输出数组 a a a和数组 b b b中的元素每个输出一行且用不用元素之间用空格隔开 这里的 n 128 n128 n128非常重要 128 8 × 16 1288\times 16 1288×16对于初期编程选手可能会连开两个大小为 128 128 128的数组并从下标 1 1 1开始存数据到下标 n n n导致数组越界。
理论上 如果测试数据中有 n 128 n128 n128的数据则期望条件下只要两个数组是连续开的就会结果错误
但结果是即使开大小为127的数组也还是会AC。。。开128可能是因为数组 a 128 a128 a128正好是 b [ 0 ] b[0] b[0]而 b b b是从下标 1 1 1开始使用的。但是开127还能过也许是测评姬上和本地内存开辟情况不同
到最后越界时不能AC的目标还是没能实现啊。。。ArrayBoundaryExceeded Killer Failed
最后贴个正确代码
#include bits/stdc.h
using namespace std;
#define mem(a) memset(a, 0, sizeof(a))
#define dbg(x) cout #x x endl
#define fi(i, l, r) for (int i l; i r; i)
#define cd(a) scanf(%d, a)
typedef long long ll;int a[128], b[128];
int main() {int n;cin n;for (int i 0; i n; i) {cin a[i];}for (int i 0; i n; i) {cin b[i];}int x, y;cin x y;swap(a[x - 1], b[y - 1]);for (int i 0; i n; i) {cout a[i] ;}cout endl;for (int i 0; i n; i) {cout b[i] ;}return 0;
}The Real End, Thanks! 原创不易转载请附上原文链接哦~ Tisfyhttps://letmefly.blog.csdn.net/article/details/135256408
