A. Extra-terrestrial Intelligence

最新推荐文章于 2024-06-27 10:37:12 发布

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最新推荐文章于 2024-06-27 10:37:12 发布

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分类专栏： codeforces A题

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本文介绍了一种用于识别外星智能信号的简单算法。该算法通过记录连续接收信号的时间间隔来判断是否存在规律性，以此推测是否有可能来自高级文明。文章包含了一个具体的实现案例，详细解释了如何从输入数据中提取规律并进行判断。

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A. Extra-terrestrial Intelligence

time limit per test

2 seconds

memory limit per test

64 megabytes

input

input.txt

output

output.txt

Recently Vasya got interested in finding extra-terrestrial intelligence. He made a simple extra-terrestrial signals’ receiver and was keeping a record of the signals for n days in a row. Each of those n days Vasya wrote a 1 in his notebook if he had received a signal that day and a 0 if he hadn’t. Vasya thinks that he has found extra-terrestrial intelligence if there is a system in the way the signals has been received, i.e. if all the intervals between successive signals are equal. Otherwise, Vasya thinks that the signals were sent by some stupid aliens no one cares about. Help Vasya to deduce from the information given by the receiver if he has found extra-terrestrial intelligence or not.

Input

The first line contains integer n (3?≤?n?≤?100) — amount of days during which Vasya checked if there were any signals. The second line contains n characters 1 or 0 — the record Vasya kept each of those n days. It’s guaranteed that the given record sequence contains at least three 1s.

Output

If Vasya has found extra-terrestrial intelligence, output YES, otherwise output NO.

Sample test(s)
input
8
00111000
output
YES
input
7
1001011
output
NO
input
7
1010100
output
YES

/* ***********************************************
Author        :
Created Time  :2015/6/15 2:01:40
File Name     :7.cpp
************************************************ */
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <iomanip>
#include <list>
#include <deque>
#include <stack>
#define ull unsigned long long
#define ll long long
#define mod 90001
#define INF 1<<30
#define maxn 10000+10
#define cle(a) memset(a,0,sizeof(a))
const ull inf = 1LL << 61;
const double eps=1e-5;
using namespace std;

bool cmp(int a,int b){
    return a>b;
}
int len;
int main()
{
    //#ifndef ONLINE_JUDGE
    freopen("input.txt","r",stdin);
    //#endif
    freopen("output.txt","w",stdout);
    int n;
	string s;
	while(cin>>n){
		cin>>s;
		int x=-1,mark=0;
		for(int i=0;i<n;i++){
			if(s[i]=='1'){
				x=i;
				for(int j=i+1;j<n;j++){
					if(s[j]=='1'){
						len=j-i;mark=1;break;
					}
				}
			}
			if(mark)break;
		}
		//cout<<len<<endl;

		int i;
		for( i=x+1;i<n;i++){
			if(s[i]=='1'){
				if((i-x)!=len)break;
				else x=i;
			}
		}
		//cout<<i<<endl;
		if(i!=n||x==-1)cout<<"NO"<<endl;
		else puts("YES");
	}
    return 0;
}