目录

模拟实现strlen

模拟实现strcpy

模拟实现strcmp

模拟实现strcat

模拟实现strstr

模拟实现memcpy

模拟实现memmove

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模拟实现strlen

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>int MyStrlen(char* str)
{int len = 0;while (str[len] != '\0')len++;return len;
}int main()
{char str[50] = { "Hello,world!" };int ans = MyStrlen(str);printf("%d\n", ans);return 0;
}

模拟实现strcpy

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>char* MyStrcpy(char* str2, char* str1)
{char* p = str2;while (*p++ = *str1++);return str2;
}int main()
{char str1[50] = { "Hello,world!" };char str2[50];MyStrcpy(str2, str1);printf("%s\n", str2);return 0;
}

模拟实现strcmp

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>int MyStrcmp(const char* str1, const char* str2)
{int i = 0;while (str1[i] != '\0' && str2[i] != '\0' && str1[i] == str2[i])i++;return str1[i] - str2[i];
}int main()
{const char* str1 = "apple";const char* str2 = "banana";const char* str3 = "apple";int ans1 = MyStrcmp(str1, str2);int ans2 = MyStrcmp(str1, str3);printf("%d\n%d", ans1, ans2);return 0;
}

模拟实现strcat

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>char* MyStrcat(char* str1, const char* str2)
{char* re = str1;while (*str1)str1++;while (*str2){*str1 = *str2;str1++;str2++;}*str1 = '\0';return re;
}int main()
{char str1[50] = "Hello,";const char* str2 = "world!";printf("%s\n", MyStrcat(str1, str2));return 0;
}

模拟实现strstr

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>char* MyStrstr(const char* str1, const char* str2)
{if (*str2 == '\0')return (char*)str1;while (*str1){const char* s1 = str1;const char* s2 = str2;while (*s1 && *s2 && (*s1 == *s2)){s1++;s2++;}if (*s2 == '\0')return (char*)str1;str1++;}return NULL;
}int main()
{const char* str1 = "Hello world";const char* str2 = "world";char* ans = MyStrstr(str1, str2);if (ans)printf("%ld\n", ans - str1);elseprintf("没找到\n");return 0;
}

模拟实现memcpy

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>void* MyMemcpy(void* brr, const void* arr, size_t size)
{char* b = (char*)brr;const char* a = (const char*)arr;for (size_t i = 0; i < size; i++)b[i] = a[i];return brr;
}int main()
{int arr[] = { 1, 2, 3, 4, 5 };int brr[5] = { 0 };MyMemcpy(brr, arr, sizeof(brr));int size = sizeof(brr) / sizeof(brr[0]);for (int i = 0; i < size; i++){printf("%d ", brr[i]);}return 0;
}

模拟实现memmove

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>
#include <string.h>
#include <cassert>void* MyMemmove(void* dest, const void* src, size_t size)
{assert(dest && src);char* ret = (char*)dest;if (dest < src){while (size--){*(char*)dest = *(char*)src;dest = (char*)dest + 1;src = (char*)src + 1;}}else if (dest > src){while (size--){*((char*)dest + size) = *((char*)src + size);}}return ret;
}int main()
{int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9,10 };MyMemmove(arr + 3, arr, 20);for (int i = 0; i < 10; i++){printf("%d ", arr[i]);}return 0;
}

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感谢大佬支持！！！