strcmp作用是比较两个字符串
是按照内容比，就是ASCII码值比较，逐对比较
This function starts comparing the first character of each string. If they are equal to each other, it continues with the following pairs until the characters differ or until a terminating null-character is reached.
头文件为<string.h>
int strcmp( const char* prt1, const char* prt2 );
/<0 the first character that does not match has a lower value in ptr1 than in ptr2
/0 the contents of both strings are equal
/>0 the first character that does not match has a greater value in ptr1 than in ptr2
上面是返回值的规则
我们下面来模拟实现一下
#include<assert.h>
#include<stdio.h>
int my_strcmp(const char* arr1,const char* arr2)
{assert(arr1 && arr2);while (*arr1 || *arr2){if (*arr1 == *arr2){arr1++;arr2++;}else return *arr1 - *arr2;}return 0;
}
int main()
{char arr1[20] = { "hello world" };char arr2[20] = { "hello world" };int ret = my_strcmp(arr1, arr2);if (ret < 0){printf("arr1小于arr2");}else if (0 == ret){printf("arr1等于arr2");}else{printf("arr1大于arr2");}return 0;
}