模拟实现strcpy,strcat,strcmp

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#define _CRT_SECURE_NO_WARNINGS 1#include<stdio.h>#include<assert.h>char *my_strcpy(char *str, const char *arr){char *ret = str;assert(str);assert(arr);while (*str++ = *arr++){;}return ret;}int main(){char arr[] = "abcde";char str[64];my_strcpy(str, arr);printf("%s\n", str);system("pause");return 0;}

strcat

char *my_strcat(char *dest, const char*src){char *ret = dest;assert(dest != NULL);assert(src != NULL);while (*dest){dest++;}while ((*dest++ = *src++)){;}return ret;}int main(){char arr[] = "abcde";char str[]="1234";my_strcat(str, arr);printf("%s\n", str);system("pause");return 0;}

strcmp

#include<stdio.h>#include<assert.h>int mystrcmp(const char *src, const char *dst){assert(src);assert(dst);int ret = 0; while (!(ret = *(unsigned char *)src-*(unsigned char *)dst) && *dst){src++;dst++;}if (ret > 0)return 1;else if (ret < 0)return -1;return 0;}int main(){char str[] = "abcde2";char arr[] = "abcde";int ret = mystrcmp(str, arr);printf("%d\n", ret);system("pause");return 0;}

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