字符串转换成整数

#include <stdio.h>

const int INT_MAX = (int)((unsigned)~0 >> 1);
const int INT_MIN = -(int)((unsigned)~0 >> 1) - 1;

int StrToInt(const char *str)
{
	if (str == NULL)
	{
		printf("The string is null!");
		exit(1);
	}
	int num = 0;
	if (str[0] != ‘-‘ && str[0] == ‘+‘ || (str[0] -‘0‘ <=9 && str[0] - ‘0‘ >=0))
	{
		for (int i = 0; str[i] != ‘\0‘; ++i)
		{
			if (str[i] - ‘0‘ <= 9 && str[i] - ‘0‘ >= 0)
			{
				if (num > INT_MAX / 10 || (num == INT_MAX / 10 && (str[i] - ‘0‘) > INT_MAX % 10))
				{
					num = INT_MAX;
					break;
				}
				else{
					num *= 10;
					num += (str[i] - ‘0‘);
				}
			}
			else{
				printf("Having a wrong with input!");
				exit(1);
			}
		}
	}
	else if (str[0] == ‘-‘){
		for (int i = 1; str[i] != ‘\0‘; ++i)
		{
			if (str[i] - ‘0‘ <= 9 && str[i] - ‘0‘ >= 0)
			{
				if (num < INT_MIN / 10 || (num == INT_MIN / 10 && (str[i] - ‘0‘) > -(INT_MIN % 10)))
				{
					num = INT_MIN;
					break;
				}
				else{
					num *= 10;
					num -= (str[i] - ‘0‘);
				}
			}
			else{
				printf("Having a wrong with input!");
				exit(1);
			}
		}
	}
	else{
		printf("It‘s wrong!");
		exit(1);
	}
	return num;
}