将字符串转化为整形

#include<stdio.h>
#include<limits.h>//头文件定义最大最小的整形
#include<iostream>//包含system函数
using namespace std;
int StrToInt(const char* str)//字符型数组转换成整形
{
    
    
	if (str == NULL || *str == '\0')
	{
    
    
		return 0;
	}	
	long long num = 0;
	int sign = 1;
	while (*str == ' ')//遇到空格就跳过
	{
    
    
		str++;
	}
	if (*str == '+')//遇到‘+’表示是整数
	{
    
    
		str++;
	}
	else if (*str == '-')//遇到‘-’表示是负数
	{
    
    
		str++;
		sign = -1;
	}
	while (*str != '\0')
	{
    
    
		if (*str >= '0'&&*str <= '9')
		{
    
    
			num = num * 10 + (*str - '0')*sign;
			if (num >= INT_MAX)
			{
    
    
				return INT_MAX;
			}
			else if (num <= INT_MIN)
			{
    
    
				return INT_MIN;
			}
		}
		else
		{
    
    
			break;
		}
		str++;
	}
	return (int)num;//注意将返回值转换为int型
}
int main()
{
    
    
	char str1[] = "  +125874";
	char str2[] = "-789546";
	char str3[] = "4587q";
	char str4[] = "qq456";
	char str5[] = "0";
	char str6[] = "12345678941123456789";
	char str7[] = "  -1245678941253647845612";
	char str8[] = "\0";
	printf("%d\n", StrToInt(str1));
	printf("%d\n", StrToInt(str2));
	printf("%d\n", StrToInt(str3));
	printf("%d\n", StrToInt(str4));
	printf("%d\n", StrToInt(str5));
	printf("%d\n", StrToInt(str6));
	printf("%d\n", StrToInt(str7));
	printf("%d\n", StrToInt(str8));
	system("pause");
	return 0;
}