Question

杭电ACM1019题求教 为什么老是wrong answer？？ 明明答案是对的啊。。

求最小公倍数
Input
Input will consist of multiple problem instances. The first line of the input will contain a single integer indicating the number of
problem instances. Each instance will consist of a single line of the form m n1
n2 n3 ... nm where m is the number of integers in the set and n1 ... nm are the
integers. All integers will be positive and lie within the range of a 32-bit
integer.

我的代码是
#include<stdio.h>
int LCM(int a,int b)
{
int t,s;
s=a*b;
if(a<b)
{
t=a;
a=b;
b=t;
}
while(a%b!=0)
{
t=b;
b=a%b;
a=t;
}
return s/b;
}
void main ()
{
int a,b,n1,n2;
scanf("%d",&n1);
while(n1--)
{
scanf("%d",&n2);
scanf("%d",&a);
n2--;
while(n2--)
{
scanf("%d",&b);
a=LCM(a,b);
}
printf("%d\n",a);
}
}

Answer 1

All integers will be positive and lie within the range of a 32-bit
integer.

说明了a和b都是32位的数据

int LCM(int a,int b)
{
int t,s; //s的最大值只可能是(2^31) - 1
s=a*b; //这里可能会溢出,
//因为如果a和b都是 (2^31) - 1这个数值，那么他们两个相乘的话，
//结果会大于2^31 - 1, 一定会溢出, 溢出意味着出错
if(a<b)
{
t=a;
a=b;
b=t;
}

ps:若有不明白的地方，可以追问