字符串转化成int

将str转化成int

#include<stdio.h>
#include<string>
int err = 0;
int str_to_int(char *s)
{
    long sum = 0;
    bool isPositive = true;
    bool isZeroStart = true;
    bool flag = false;
    char c;
    int maxInt = 0x7fffffff;
    bool flag2;
    bool isNumStart = false;

    while (*s != '\0') {
	c = *s;
	flag = (c >= '0' && c <= '9');

	if (c == '-') {
	    if (isNumStart) {
		err = 9;
		printf("- is illegal");
		return -1;
	    }
	    isPositive = false;
	    s++;
	} else if (c == '0' && isZeroStart) {
	    isNumStart = true;
	    s++;

	} else if (c == '+') {
	    if (isNumStart) {
		err = 9;
		printf("+ is illegal");
		return -1;
	    }

	    if (*(s + 1) == '\0') {
		err = 10;
		printf("num is +\n");
		return -1;
	    }
	    flag2 = (*(s + 1) >= '0' && *(s + 1) <= '9');
	    if (!flag2) {
		err = 11;
		printf("num is ilegal\n");
		return -1;
	    }
	    ++s;
	} else if (flag) {
	    sum = sum * 10 + c - '0';
	    isNumStart = true;
	    if (sum >= maxInt) {
		break;
	    }
	    isZeroStart = false;
	    ++s;
	} else {
	    err = 11;
	    printf("num is ilegal\n");
	    return -1;

	}

    }
    if (isPositive) {
	return sum;
    }
    return -sum;
}

int main(int argc, char *argv[])
{

    if (argc != 2) {
	printf("input num please\n");
	return -1;
    }

    char *str = argv[1];
    int num = str_to_int(str);

    if (err) {
	printf("parse str to num is err\n ");
	return -1;
    }
    printf("num = %d\n", num);
    return 0;
}

该程序支持+，-开头，允许000开头