c语言 11-10

1、strtoi

#include <stdio.h>

int strtoi(const char *s)
{
    int i, j = 0;
    while(*s)
    {
        for(i = 0; i <= 9; i++)
        {
            if(*s - '0' == i)
                j = j * 10 + i;
        }
        s++;
    }
    return j;
}

int main(void)
{
    char str[128];
    printf("str:  "); scanf("%s", str);
    
    printf("result afrer concersion: %d
", strtoi(str));
    return 0;
}

2、

#include <stdio.h>

long strtol(const char *s)  //??????????????????
{
    int i;
    long j = 0;
    while(*s)
    {
        for(i = 0; i < 9; i++)
        {
            if(*s - '0' == i)
                j = j * 10 + (long)i;
        }
        s++;
    }
    return j;
}

int main(void)
{
    char str[128];
    printf("str: "); scanf("%s", str);
    
    printf("result after conversion: %d
", strtol(str));
    return 0;
}

3、

#include <stdio.h>

double strtof(const char *s)
{
    int i;
    double j = 0.0;
    while(*s)
    {
        for(i = 0; i <= 9; i++)
        {
            if(*s - '0' == i)
                j = j * 10 + (double)i;
        }
        s++;
    }
    return j;
}

int main(void)
{
    char str[128];
    printf("str: "); scanf("%s", str);
    
    printf("result after conversion: %f
", strtof(str));
    return 0;
}