国外产品设计网站推荐,用ps做企业网站分辨率是多少,详情页设计流程,容桂网站建设联系方式本帖最后由 奉聪 于 2017-1-25 14:54 编辑*******前言*******我数一下#xff0c;我发了几个帖子#xff0c;1、2、3#xff1f;哈哈哈#xff0c;没几个哈#xff0c;感谢吾爱#xff0c;让我学到了很多#xff0c;乐于分享#xff0c;共同进步#xff01;最近也是在…本帖最后由 奉聪 于 2017-1-25 14:54 编辑*******前言*******我数一下我发了几个帖子1、2、3哈哈哈没几个哈感谢吾爱让我学到了很多乐于分享共同进步最近也是在学c语言也看了少许面试题指针数据结构字符串操作肯定是重点今天分享出来的是一些字符串操作函数和一些内存操作函数的手动实现内容应该不难如有错误还请朋友们指出我会认真改正的希望一起学习进步*******目录*******字符串常见函数strlen、strcmp、strcpy、strlwr、strrev、strset、strstr、strupr、itoa、atoi、atof、ftoa(希望初学者能够尝试用下标访问和指针访问两种方式实现)内存操作少许函数memccpy、memchr、memcpy、memicmp、memmove、memset(希望读者能够认真手动实现)当然实际开发中这些函数直接调用就行了但是面试的时候这是基础知识这是考察你的基本功 和 砍你工资的大斧因为简单所以代码注释少有疑惑的请告诉我乐于交流*******字符串函数*******1.strlen计算字符串长度(不包含\0)实现想法遍历字符串直到\0结束[C] 纯文本查看 复制代码#include#include#include//指针法unsigned int mystrlenaddr(const char * str) //为什么使用const char我们只计数不对原数据进行改变{int length 0; //长度初始化为0while (*str){length;}return length;}void main(){char * str fengcong is fucking too handsome; //32个//printf(%d\n, strlen(str));printf(%d\n, mystrlenaddr(str));system(pause);}2.strcmp比较字符串大小(一般用于字符串排序)实现想法依次从字符串开始一直找到不同的那个字符进行比较得出大小[C] 纯文本查看 复制代码#include#include#include//掌握指针法int mystrcmp(char const * str1, const char * str2){while (*str1 *str2 *str1 ! 0) //一直找到两个字符串不同的地方{str1;str2;}if (*str1 *str2)return 1;else if (*str1 *str2)return -1;elsereturn 0;}void main(){char * str feng1;char * str1 feng2;//printf(%d\n, strcmp(str, str1));printf(%d\n, mystrcmp(str, str1));system(pause);}3.strcpy用于字符串复制(复制包含\0)实现想法一直复制到\0结束[C] 纯文本查看 复制代码#define _CRT_SECURE_NO_WARNINGS#include#include#include//指针法char * mystrcpyaddr(char * dest, const char * source){if (dest NULL || source NULL){return NULL; //如果目的操作或者源为空那么久直接返回}while (*dest *source) //装X写法;return dest;}//下标法char * mystrcpyindex(char * dest, const char * source){if (dest NULL || source NULL){return NULL; //如果目的操作或者源为空那么久直接返回}int i 0;while (source ! \0){dest source;i;}dest source; //因为要把最后的\0拷贝过去return dest;}void main(){char * str fengcong is fucking too handsome;char str1[100]; //目的字符数组//strcpy(str1, str);//printf(%s\n, str1);mystrcpyindex(str1, str);printf(%s\n, str1);system(pause);}4.strlwr:大写转小写实现想法遍历字符串遇到大写转为小写[C] 纯文本查看 复制代码#include#include#includechar * mystrlwr(char * str){char * p1 str;while (*p1){if (*p1 A *p1 Z){*p1 32;}p1;}return str;}void main(){char str[50] FENGCONG IS FUCKING TOO HANDSOME;//printf(%s\n, _strlwr(str));printf(%s\n, mystrlwr(str));system(pause);}5.strrev字符串逆转实现想法头首交换直到中间[C] 纯文本查看 复制代码#include#include#includechar * mystrrev(char * str){char * p2 str;char * p1 str;while (*p1){;}p1 - 2; //回到最后一个字符while (p1 - p2 1){char temp *p1;*p1 *p2;*p2 temp;p2;p1--;}return str;}void main(){char str[50] fengcong is fucking too handsome;//_strrev(str);//printf(%s\n, str);printf(%s\n,mystrrev(str));system(pause);}6.strset将字符串全部设成某字符实现想法遍历字符串每个字符设置某字符直至\0[C] 纯文本查看 复制代码#define _CRT_SECURE_NO_WARNINGS#include#include#includechar * mystrset(char * str, int value){char * p1 str;while (*p1){*p1 value;p1;}return str;}void main(){char str[50] fengcong is fucking too handsome;//printf(%s\n, _strset(str, A));printf(%s\n, mystrset(str, A));system(pause);}7.strstr寻找母串中是否存在某个子串(稍难)实现想法依次比对[C] 纯文本查看 复制代码#include#include#include//下标 法char * mystrstrindex(char * const momstr, const char * const sonstr)//前者指针指向的数据可变但是指针不可变后者都不可变{int momlen strlen(momstr); //母串的长度int sonlen strlen(sonstr); //子串的长度for (int i 0; i (momlen - sonlen); i) //从0开始循环母串到momlen-sonlen停止{int flag 1;for (int j 0; j sonlen; j){if (momstr[i j] ! sonstr[j]){flag 0;break; //如果出现不相等就 退出循环继续从下面一个寻找}}if (flag){return (momstr);}}return NULL;}//指针法char * mystrstraddr(char * const momstr, const char * const sonstr){char * mstr momstr; //母串while (*mstr){char * sstr sonstr; //子串char * momnowstr mstr; //记录现在母串的位置int flag 1;while (*sstr ! 0){if (*sstr ! *momnowstr || *momnowstr 0){flag 0;break;}momnowstr;sstr;}if (flag){return mstr;}mstr; //母串对比位置1}return NULL;}void main(){char * str fengcong is too fucking handsome;//printf(%p, strstr(str, fengcong));//printf(%p, mystrstrindex(str, engcong));printf(%p, mystrstraddr(str, some));system(pause);}8.strupr:小写转大写实现想法依次遍历遇到小写转为大写[C] 纯文本查看 复制代码#define _CRT_SECURE_NO_WARNINGS#include#include#includechar * mystrupr(char * str){char * p1 str;while (*p1){if (*p1 a *p1 z){*p1 - 32;}p1;}return str;}void main(){char str[50] fengcong is fucking too handsome;//printf(%s\n, _strupr(str));printf(%s\n, mystrupr(str));system(pause);}9.itoa:整数转字符串[C] 纯文本查看 复制代码#define _CRT_SECURE_NO_WARNINGS#include#include#includechar * myitoa(int value, char * str){char * pstr str; //str本身不能改变一会要返回strif (value 0){*pstr -;pstr;value * -1; //转变为正数处理}int wei 1; //数至少一位int ivalue value; //用于测试长度while ((ivalue / 10) ! 0){wei;}pstr wei-1;while (value % 10 ! 0){*pstr-- (value % 10)0;value / 10;}return str;}void main(){int num -45644;char str[20] { 0 };printf(%s, myitoa(num, str));system(pause);}10.atoi字符串转整数(遇到非数字字符结束)[C] 纯文本查看 复制代码#include#include#includeint myatoi(const char * str){if (str NULL){return 0;}int num 0; //需要返回的值int flag 1; //记录正负号if (*str -){flag -1;str;}else if (*str ){str;}while (*str 0 *str 9){num (num * 10 (*str - 0));str;}return num*flag;}void main(){char str[20] -57124;int num 0;printf(%d\n,myatoi(str));system(pause);}11.atof:字符串转浮点数[C] 纯文本查看 复制代码#include#include#includedouble myatof(char const * str){if (str NULL)return 0;//首先判断有无符号位int flag 1;if (*str -){flag -1;str;}if (*str ){str;}int zhengshu 0; //存储整数部分while (*str 0 *str 9){zhengshu zhengshu * 10 (*str - 0);*str;}//整数部分循环完了double xiaoshu 0.0; //存储小数部分//因为不明符号停止整数循环if (*str ! .){return (flag * zhengshu);}else //代表遇到. 结束{str; //指向小数部分第一位double i 0.1;while (*str 0 *str 9){xiaoshu xiaoshu (*str - 0)*i;i / 10;str;}return flag *(zhengshu xiaoshu);}}void main(){char str[20] 2.1554;double db 0.0;printf(%lf\n, myatof(str));system(pause);}12.ftoa浮点数转字符串(浮点数存储不准确可能有少许误差)[C] 纯文本查看 复制代码#include#include#includechar * myftoa(double db, char * str){char * pstr str;//先判断 符号位if (db 0){*pstr -;db * -1; //转为正数处理pstr;}//整数部分int zhengshu (int)db;int izhengshu zhengshu; //牺牲于记录整数长度int wei 1; //整数部分至少一位while ((izhengshu / 10) ! 0){wei;}pstr wei - 1;for (int i 0; i wei; i){*pstr-- zhengshu % 10 0;zhengshu / 10;}pstr (wei1);*pstr .;pstr;//小数部分double xiaoshu db - (int)db;for (int i 0; i 6; i){*pstr (int)(xiaoshu * 10) 0;xiaoshu xiaoshu * 10 - (int)(xiaoshu * 10);}return str;}void main(){double db -2.11;char str[20] { 0 };printf(%s\n, myftoa(db,str));system(pause);}*******内存操作函数*******1.memccpy内存拷贝直到一个值结束[C] 纯文本查看 复制代码#include#include#include//下标法void * mymemccpybyindex(void * dest, const void * sor,int val, size_t len){if (dest NULL || sor NULL){return NULL;}for (int i 0; i len; i){if( (((char*)dest) ((char*)sor)) val)return dest;}return dest;}//指针法void * mymemccpybyaddr(void * dest, const void * sor,int val, size_t len){if (dest NULL || sor NULL){return NULL;}char * pdest dest;char * psor sor;char * plast (char *)sor len;while (psor plast){if ((*pdest *psor) val)return dest;}return dest;}void main(){char str[50] fengcong is fucking too handsome;char * pstr (char[50]) { 0 }; //在栈上开辟一段内存//printf(%s\n, memccpy(pstr,str,s,32));printf(%s\n, mymemccpybyaddr(pstr, str, f, 32));system(pause);}2.memchr:某段内存中寻找某个值[C] 纯文本查看 复制代码#include#include#includevoid * mymemchar(void * buf, int val, size_t size){if (buf NULL){return NULL;}char * p buf;char plast p size;while (p plast){if (*p val){return p;}p;}return NULL;}void main(){char str[50] fengcong is fucking too handsome;printf(%s\n, mymemchar(str, g, 8));system(pause);}3.memcpy:拷贝某段内存[C] 纯文本查看 复制代码#include#include#include//下标法void * mymemcpybyindex(void * dest, const void * sor, size_t len){if (dest NULL || sor NULL){return NULL;}for (int i 0; i len; i){((char*)dest) ((char*)sor);}return dest;}//指针法void * mymemcpybyaddr(void * dest, const void * sor, size_t len){if (dest NULL || sor NULL){return NULL;}char * pdest dest;char * psor sor;char * plast (char * )sor len;while (psor plast){*pdest *psor;}return dest;}void main(){char str[50] fengcong is fucking too handsome;char * pstr (char[50]) { 0 }; //在栈上开辟一段内存//printf(%s\n, memcpy(pstr, str, 32));printf(%s\n, mymemcpybyaddr(pstr, str, 31));system(pause);}4.memicmp:比较某段内存大小(一个字节一个字节比较像strcmp)注意切不可用来比较整数除非一字节整数因为整数存储方式是高位高字节[C] 纯文本查看 复制代码#include#include#includeint mymemicmpbyaddr(const void * buf1, const void * buf2, size_t size){char * p1 buf1;char * p2 buf2;int i 0;while(*p1 *p2 i size){p1;p2;i;}if (*p1 *p2){return 1;}else if (*p1 *p2)return -1;elsereturn 0;}void main(){char str[50] fengcong is fucking too handsome;char str1[50] fengfeng is fucking too handsome;printf(%d\n, mymemicmpbyaddr(str, str1, 32));system(pause);}5.memmove和memcpy类似但是memmove采用了中间空间memcpy是直接拷贝两者区别之处在于当拷贝地址重复的时候结果不一样(比较代码可知)[C] 纯文本查看 复制代码#include#include#include#includevoid * mymemmove(void * dest, const void * sor, size_t size){char * ptemp malloc(size); //中间 地址memcpy(ptemp, sor, size);memcpy(dest, ptemp, size);free(ptemp);}void main(){char str[50] fengcong is fucking too handsome;//memmove(str 3, str 4, 2);mymemmove(str 3, str 4, 2);printf(%s\n,str);system(pause);}6.memset对指定内存每个字节赋某个值[C] 纯文本查看 复制代码#include#include#include//下标法void * mymemsetbyindex(void * dest, int val, size_t len){if (dest NULL){return NULL;}if (len 0){return dest;}char * p dest;for (int i 0; i len; i){p val;}return dest;}//指针法void * mymemsetbyaddr(void * dest, int val, size_t len){if (dest NULL){return NULL;}if (len 0){return dest;}char * p dest;char * plast p len;while (p plast){*p val;}return dest;}void main(){char str[50] fengcong is fucking too handsome;//printf(%s\n, memset(str, 65, 8));printf(%s\n, mymemsetbyaddr(str, 65, 8));system(pause);}*******结束语*******内容应该都不难希望大家讨论讨论认真实现不要让这基本功成为面试官挥动大斧砍你工资的把柄文中代码区少许地方少*不知道为什么请注意添加再会了还是那句话你们开心就好拜个早年ω
