自定义方法实现strcpy,strlen, strcat, strcmp函数,了解及实现原理

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unsigned long myStrlen(char string[])
{
    unsigned long length = 0;
    
    while (string[length] != ‘\0‘) {
        length++;
    }
    
    return length;
}

void myStrcpy(char string1[], char string2[])
{
    int i = 0;
    while (string2[i] != ‘\0‘) {
        string1[i] = string2[i];
        i++;
    }
    string1[i] = ‘\0‘;
}

void myStrcat(char string1[], char string2[])
{
    //找string1的‘\0‘位置
    int i = 0;
    while (string1[i] != ‘\0‘) {
        i++;
    }
    
    //把string2加到string1后面
    int j = 0;
    while (string2[j] != ‘\0‘) {
        string1[i++] = string2[j++];
    }

//不要忘记在最后添加\0
    string1[i] = ‘\0‘;
}

int myStrcmp(char string1[], char string2[])
{
    int i = 0;
    while (string1[i] == string2[i] && string1[i] != ‘\0‘) {
        i++;
    }
    
    return string1[i] - string2[i];
}

自定义方法实现strcpy,strlen, strcat, strcmp函数,了解及实现原理

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原文地址：http://www.cnblogs.com/tian-sun/p/4307519.html