比较两个字符串

用数组名作形参

#include <iostream>
#include <string.h>
using namespace std;
int astrcmp(const char str1[], const char str2[]);
int main()
{
    char s1[50]="Hello world. ";
    char s2[50]="Good morning! ";
    switch (astrcmp(s1,s2))
    {
    case 0:
        cout<<"s1与s2相等";
        break;
    case 1:
        cout<<"s1大于s2";
        break;
    case 3:
        cout<<"s1小于s2";
        break;
    }
    return 0;
}
int astrcmp(const char str1[], const char str2[])
{
    int i=0,n;
    while(1)
    {
        if(str1[i]!='\0'&&str2[i]!='\0')
        {
            if(str1[i]==str2[i])
            {
                n=0;
                i++;
            }
            else
            {
                if(str1[i]>str2[i])
                {
                    n=1;
                }
                else
                {
                    n=2;
                }
                break;
            }
        }
        else
        {
            if(str1=='\0')
            {
                n=2;
            }
            else
            {
                n=1;
            }
            break;
        }
    }
    return n;
}

 

用指针作形参

#include <iostream>
#include <string.h>
using namespace std;
int astrcmp(const char *, const char *);
int main()
{
    char s1[50]="Hello world. ";
    char s2[50]="Good morning! ";
    switch (astrcmp(s1,s2))
    {
    case 0:
        cout<<"s1与s2相等";
        break;
    case 1:
        cout<<"s1大于s2";
        break;
    case 3:
        cout<<"s1小于s2";
        break;
    }
    return 0;
}
int astrcmp(const char *str1, const char *str2)
{
    int i=0,n;
    while(1)
    {
        if(*(str1+i)!='\0'&&*(str2+i)!='\0')
        {
            if(*(str1+i)==*(str2+i))
            {
                n=0;
                i++;
            }
            else
            {
                if(*(str1+i)>*(str2+i))
                {
                    n=1;
                }
                else
                {
                    n=2;
                }
                break;
            }
        }
        else
        {
            if(*(str1+i)=='\0')
            {
                n=2;
            }
            else
            {
                n=1;
            }
            break;
        }
    }
    return n;
}