字符串转整数

c语言字符串转换整数

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define bool _Bool
#define true 1
#define false 0
bool strToInt(char *s, long *num)
{
    bool minus = false;
    bool first = true;
    while(*s != '\0'){
        if (*s == '+' && first) {
            s++;
        } else if(*s == '-' && first) {
            minus = true;
            s ++;
        } else {
            first = false;
            if (*s < '0' || *s >'9')
            {
                printf("The string is not Int num\n");
                return false;
            }
            *num = *num *10 + (*s-'0');
            s ++;
        }
    }
    if (minus) {
        *num = 0 - *num;
    }
    return true;
}

int main()
{
    char *s = "-123";
    long num = 0;
    if(strToInt(s, &num)) {
        printf("num = %ld\n", num);
    }
}

实际上，c 语言库中有此函数atoi()

    char *c = "345";

    printf("c = %d\n", atoi(c));