zoukankan      html  css  js  c++  java
  • CF w4d1 B. Petya and Staircases

    Little boy Petya loves stairs very much. But he is bored from simple going up and down them — he loves jumping over several stairs at a time. As he stands on some stair, he can either jump to the next one or jump over one or two stairs at a time. But some stairs are too dirty and Petya doesn't want to step on them.

    Now Petya is on the first stair of the staircase, consisting of n stairs. He also knows the numbers of the dirty stairs of this staircase. Help Petya find out if he can jump through the entire staircase and reach the last stair number n without touching a dirty stair once.

    One has to note that anyway Petya should step on the first and last stairs, so if the first or the last stair is dirty, then Petya cannot choose a path with clean steps only.

    Input

    The first line contains two integers n and m (1 ≤ n ≤ 10^9, 0 ≤ m ≤ 3000) — the number of stairs in the staircase and the number of dirty stairs, correspondingly. The second line contains m different space-separated integers d 1, d 2, ..., d m (1 ≤ d i ≤ n) — the numbers of the dirty stairs (in an arbitrary order).

    Output

    Print "YES" if Petya can reach stair number n, stepping only on the clean stairs. Otherwise print "NO".

    Examples

    inputCopy
    10 5
    2 4 8 3 6
    outputCopy
    NO

    inputCopy
    10 5
    2 4 5 7 9
    outputCopy
    YES

    小男孩一次可以跳一格或者两格或者三格,要是有三个连续的脏楼梯就过不去了。有三个特判:第一个楼梯是脏的或者最后一个楼梯是脏的或者没有脏楼梯。

    #include<bits/stdc++.h>
    using namespace std;
    int f[3005];
    int n,m;
    bool ans=true;
    
    int main()
    {
    	cin>>n>>m;
    	for(int i=0;i<m;i++)cin>>f[i];
    	sort(f,f+m);
    	if(f[0]==1||f[m-1]==n||m==0){//特判
    		if(m==0)cout<<"YES"<<endl;
    		else cout<<"NO"<<endl;
    		return 0;
    	}
    	for(int i=0;i<m-2;i++){
    		if(f[i]=f[i+1]-1&&f[i]==f[i+2]-2){//连续3个脏楼梯
    			ans=false;
    			break;
    		}
    	}
    	if(ans)cout<<"YES"<<endl;
    	else cout<<"NO"<<endl;
    	return 0;
    }
    
  • 相关阅读:
    POJ 2593&&2479:Max Sequence
    POJ 2115:C Looooops
    杭电2187--悼念512汶川大地震遇难同胞——老人是真饿了
    南阳448--寻找最大数
    杭电2544--最短路(Floyd)邻接表使用方法模板
    杭电2141--Can you find it?
    杭电1242--Rescue(BFS+优先队列)
    杭电1241--Oil Deposits(Dfs)
    南阳42--一笔画问题
    杭电1950--Bridging signals (二分法→ →LIS)
  • 原文地址:https://www.cnblogs.com/LiangYC1021/p/12960760.html
Copyright © 2011-2022 走看看