C的字符串操作函数实现

柔情只为你懂 2022-05-30 20:41 211阅读 0赞

strlen函数实现:

int MyStrlen(char * str){
        if(str == NULL)
            return -1;
        int count = 0;
        while(*str++ != '\0'){
            count ++;
        }
        return count;
    }

strcpy函数实现:

char * MyStrcpy(char * str, const char * str2){
        int i = 0;
        while(str2[i] != '\0'){
            str[i] = str2[i];
            i++;
        }
        str[i] = '\0';
        return str;
    }

strcat函数实现:

char * MyStrcat(char * str, const char * str2){
        while(*str++ != '\0')
        ;
        str--;
        int i = 0;
        while( str2[i] != '\0'){
            str[i]= str2[i];
            i++;
        }
        str[i] = str2[i];
        return str;
    }

strcmp函数实现:

int  MyStrcmp(const char * str, const char * str2){
        int i = 0;
        while(str[i] != '\0' || str2[i] != '\0'){
            if(str[i] == '\0' || str[i] < str2[i])
                return -1;
            else if(str2[i] == '\0' || str[i] > str2[i])
                return 1;
            i++;
        }
        if(str[i] == '\0' && str2[i] == '\0')
            return 0;
    }

strchar函数实现:

int MyStrchar(const char * str, char ch){
        if(str == NULL)
            return -1;
        int index = -1;
        int i = 0;
        while(str[i] != ch && str[i] != '\0')
            i++;
        index = i;
        if(str[i] == '\0')
            return -1;
        return index;
    }

strstr函数实现:

int MyStrstr(const char * str, const char * str2){
        int index = -1;
        int i = 0;
        if(*str2 == '\0' || *str == '\0')
            return index;
        while(str[i] != '\0'){
            int j = 0;
            while(str2[j] == str[i+j] && str2[j] != '\0'){
                j++;
            }
            if(str2[j] == '\0')
                return index = i;
            i++;
        }
        if(str[i] == '\0')
            return index;
    }