POJ 2591 Set Definition

最新推荐文章于 2017-12-05 21:23:00 发布

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本文解析了一道POJ月赛的大数据题，通过使用int类型而非longlong类型解决了内存溢出问题，并提供了解题思路及AC代码实现。

一道poj以前月赛的题，数据超大，用long long 超内存，换成int 3万多K水过。。。。。。。。。这道题和上午那道纠结了一天的题是一样的，所以这道题很快就A了。水同样类型的题，很有成就感，有木有！有木有！！！！！！题目：

Set Definition

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 8248		Accepted: 3765

Description

Set S is defined as follows:
(1) 1 is in S;
(2) If x is in S, then 2x + 1 and 3x + 1 are also in S;
(3) No other element belongs to S.

Find the N-th element of set S, if we sort the elements in S by increasing order.

Input

Input will contain several test cases; each contains a single positive integer N (1 <= N <= 10000000), which has been described above.

Output

For each test case, output the corresponding element in S.

Sample Input

100
254

Sample Output

418
1461

ac代码：

#include <iostream>
#include <cstdio>
using namespace std;
const int N=100005*100;
int num[N];
int min(int a,int b){
  return a<b?a:b;
}
int main(){
  //freopen("4.txt","r",stdin);
  num[1]=1;
  int p2,p3;
  p2=p3=1;
  int i=1;
  while(i<=10000001){
    num[++i]=min(2*num[p2]+1,3*num[p3]+1);
	if(num[i]==2*num[p2]+1)
		p2++;
	if(num[i]==3*num[p3]+1)
		p3++;
  }
  int n;
  while(~scanf("%d",&n)){
    printf("%d\n",num[n]);
  }
  return 0;
}