面试基础_03实现strcpy、strcat、strcmp、strlen

/*************************************************************************
> File Name: testString.h
> Author: qiaozp
> Mail: qiaozongpeng@163.com
> Created Time: 2014-9-30 11:21:15
************************************************************************/
#include <iostream>
#include <string.h>
using namespace std;

//实现字符串拷贝
char* _strcpy(char* src, char* dst)
{
if (src == NULL)
{
return NULL;
}
char* tmp = src;
int i = 0;
while (*tmp)
{
dst[i++] = *(tmp++);
}
dst[i] = '\0';
return dst;
}

//实现字符串追加
char* _strcat(char* dst, char* src)
{
if (src == NULL)
{
return NULL;
}

char* tmp = src;
int pos = strlen(dst);
while (*tmp)
{
dst[pos++] = *(tmp++);
}
dst[pos] = '\0';

return dst;
}

//实现获取字符串长度
int _strlen(char* sz)
{
char* tmp = sz;
int i = 0;
while (*tmp)
{
++i;
++tmp;
}
return i;
}

//实现字符串比較
int _strcmp(char* srcA, char* srcB)
{
char* cmpA = srcA;
char* cmpB = srcB;
//1 按位比較大小
while ((*cmpA) && (*cmpB))
{
if (*cmpA = *cmpB)
{
++cmpA;
++cmpB;
continue;
}
else if (*cmpA > *cmpB)
{
return 1;
}
else
{
return -1;
}
}

//2 比較长度
return _strlen(srcA) - _strlen(srcB);
}

int main()
{
char* p = "you are a student.";
char e[30] = {0};
if (_strcpy(p, e) == NULL)
{
return -1;
}
cout << "拷贝后的字符串：" << e << endl;

if (_strcat(e, "name : qiao") == NULL)
{
return -1;
}
cout << "追加后的字符串：" << e << endl;

cout << _strlen(p) << endl;

cout << _strcmp("qiao", "qiap") << endl;
}