河南第五届ACM省赛（最强DE 战斗力）（找规律+大数）

题目地址：http://acm.nyist.net/JudgeOnline/problem.php?pid=541

思路：找规律题，数据开小了，直接用Java改了一下直接A了，不过Java耗时有点长啊，注意类名要写成Main，不然会编译错误

1 1
2 2
3 3
4 4
5 3*2
6 3*3
7 3*4
8 3*3*2
9 3*3*3
10 3*3*4
11 3*3*3*2
12 3*3*3*3
13 3*3*3*4
14 3*3*3*3*2
15 3*3*3*3*3
16 3*3*3*3*4

AC代码：

import java.io.*;
import java.util.*;
import java.math.BigInteger;

public class Main {

public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
int t = in.nextInt();
while(t-->0)
{
int n = in.nextInt();
if(n == 1)
{
System.out.println(1);
continue;
}
if(n == 2)
{
System.out.println(2);
continue;
}
int sum = n / 3;
int sum1 = n % 3;
BigInteger sum2 = BigInteger.ONE;
if(sum1 == 2 || sum1 == 0)
{
for(int i=1; i<=sum; i++)
{
sum2 = sum2.multiply(BigInteger.valueOf(3));
}
if(sum1 == 2)
sum2 = sum2.multiply(BigInteger.valueOf(2));
}
else
{
for(int i=1; i<sum; i++)
{
sum2 = sum2.multiply(BigInteger.valueOf(3));
}
sum2 = sum2.multiply(BigInteger.valueOf(4));
}
System.out.println(sum2);
}
}

}

错误代码：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <cstring>
#include <climits>
#include <cmath>
#include <cctype>

const int inf = 0x7f7f7f7f;//2139062143
typedef long long ll;
using namespace std;

int main()
{
int t;
int i,n;
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);
if(n == 1)
{
printf("1\n");
continue;
}
if(n == 2)
{
printf("2\n");
continue;
}
int sum = n / 3;
int sum1 = n % 3;
ll sum2 = 1;
if(sum1 == 2 || sum1 == 0)
{
for(i=1; i<=sum; i++)
{
sum2 *= 3;
}
if(sum1 == 2)
sum2 *= 2;
}
else
{
for(i=1; i<sum; i++)
{
sum2 *= 3;
}
sum2 *= 4;
}
printf("%I64d\n",sum2);
}
return 0;
}

很快就会超long long，必须得用大整数