C语言实现库函数strlen

size_t是 unsigned int
fgets会读入\n，用strcspn函数除去
assert判读指针是否为空指针，使用前要引头文件<assert.h>

#include <stdio.h>
#include <assert.h>
size_t mystrlen(const char* str)
{assert(str);size_t count = 0;while (*str != '\0'){count++;str++;}printf("%d", count);return count;
}
int main()
{   char arr[1001];fgets(arr,1001, stdin);arr[strcspn(arr,"\n")] = 0;mystrlen(arr);return 0;
}