模拟实现字符串操作

#include<stdio.h>
#include<assert.h>
#include<windows.h>
int my_strstr(char*arr1, char*arr2)//字符串查找
{
    assert(arr1&&arr2);
    int len1 = strlen(arr1);
    int  len2 = strlen(arr2);
    if (len1 < len2)
    {
        return -1;
    }
    int i, j;
    for (i = 0; i < len1-1; i++)
    {
        for (j = 0; j < len2; j++)
        {
            if (arr1[i] == arr2[j])
            {
                i++;
                if (j == len2-1)
                {
                    printf("存在\n");
                    return 1;
                }
            }
            else
            {
                break;
            }
        }
        j = 0;
    }
    printf("不存在\n");
    return 0;
}
char* my_strcyp(const char*arr1, char*arr2)//字符串拷贝
{
    if (arr1 == arr2)
    {
        return arr1;
    }
    assert(arr1&&arr2);
    int len1 = strlen(arr1);
    int len2 = strlen(arr2);
    if (len1 < len2)
    {
        printf("错误");
        return 0;
    }
    char*address = arr2;
    while (*arr1 != '\0')
    {
        *arr2 = *arr1;
        *arr2++;
        *arr1++;
    }
    *arr2 = '\0';
    printf("成功\n");
    return address;
}
char* my_strcat(char*arr1, const char*arr2)//字符串拼接
{
    assert(arr1&&arr2);
    int len1 = strlen(arr1);
    int len2 = strlen(arr2);
    char*a = arr1;
    while (*arr2 != '\0')
    {
        arr1[len1] = *arr2;
        len1++;
        *arr2++;
    }
    return a;
}


int main()
{
    char arr1[100] = "ABCAACDEF";
    char arr2[20] = "CD";
    char arr3[10] = { 0 };
    my_strstr(arr1,arr2);
    my_strcyp(arr1, arr3);
    my_strcat(arr1, arr2);
    system("pause");
    return 0;
}