字符串算法

字符串逆转

void reverse(char* str,int beg,int end)
{
    int times = (end- beg +1)/2;
    while(times > 0)
    {
        char tmp = str[end];
        str[end--] = str[beg];
        str[beg++] = tmp;
        times--;
    }
}

 字符串包含

bool is_substr(char* str1,char* str2)
{
    int i = 0,j = 0;
    while(str1[i] != '\0')
    {
        while(str2[j] != '\0' && str1[i] == str2[j] )
        {
            i++;
            j++;
        }
        if(str2[j] == '\0')
            return true;
        else
            j = 0;
        i++;
    }
    return false;
}

 strncpy

char* _strncpy(char* dest, const char* src, int len)  
{  
    assert('\0') error
    assert(dest!=NULL && src!=NULL);  

    char* temp=dest;  
    int i=0;  

    while(i++ < len  && (*temp++ = *src++)!='\0')  
    {}  

    if(*(--temp)!='\0')  
        *temp='\0';  

    return dest;  
}

strcpy

char* _strcpy(char* dest,const char* src)
{
    assert(dest!=NULL && src!=NULL);

    char* temp=dest;

    while((*temp++ = *src++ )!='\0')
    {}

    return dest;
}