HDU 5532 Almost Sorted Array （2015ACM/ICPC长春LIS）

本文主要是介绍HDU 5532 Almost Sorted Array （2015ACM/ICPC长春LIS），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

【题目链接】：click here~~

【题目描述】：

Almost Sorted Array

We are all familiar with sorting algorithms: quick sort, merge sort, heap sort, insertion sort, selection sort, bubble sort, etc. But sometimes it is an overkill to use these algorithms for an almost sorted array.

We say an array is sorted if its elements are in non-decreasing order or non-increasing order. We say an array is almost sorted if we can remove exactly one element from it, and the remaining array is sorted. Now you are given an array a1,a2,…,an , is it almost sorted?

The first line contains an integer T indicating the total number of test cases. Each test case starts with an integer n in one line, then one line with n integers a1,a2,…,an .

1≤T≤2000
2≤n≤105
1≤ai≤105
There are at most 20 test cases with n>1000 .

  
3
3
2 1 7
3
3 2 1
5
3 1 4 1 5

  
YES
YES
NO

【思路】我们考虑删除一个元素后，使得单调递增最长的序列长度满足>=n-1就可以了，单调递减的就翻转数列在操作一遍即可，复杂度(O(nlogN))

代码：

/*
* Problem:HDU 5532
* Running time: 1100MS
* Complier: G++
* Author: javaherongwei
* Create Time: 21:20 2015/11/02 星期一
*/
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
const int inf=1e9+7;
const int maxn=1e5+10;
using namespace std;
inline int max(int a,int b){return a>b?a:b;
}
int a[maxn],b[maxn],c[maxn];
int n;
int binary_search(int x){ //二分搜索int l=1,r=n;while(l<r){int mid=(l+r)>>1;if(b[mid]>x) r=mid;else l=mid+1;}return l;
}
bool LIS(const int *a){ //LISmemset(b,inf,sizeof(b));b[0]=0;int maxx=0;for(int i=1; i<=n; ++i){int idx=binary_search(a[i]);//i位置的LIS为idxmaxx=max(idx,maxx);b[idx]=a[i];}if(maxx>=n-1) return true; //满足条件即可return false;
}
int main(){//freopen("1.txt","r",stdin);int t;scanf("%d",&t);while(t--){scanf("%d",&n);for(int i=1; i<=n; ++i){scanf("%d",&a[i]);c[n-i+1]=a[i];}if(LIS(a)||LIS(c)) puts("YES");else puts("NO");}return 0;
}

这篇关于HDU 5532 Almost Sorted Array （2015ACM/ICPC长春LIS）的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！