2015长春赛 Almost Sorted Array

http://acm.hdu.edu.cn/contests/contest_showproblem.php?cid=646&pid=1006

Almost Sorted Array

Problem Description
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?
Input
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.

1T2000
2n105
1ai105
There are at most 20 test cases with  n>1000.
Output
For each test case, please output "`YES`" if it is almost sorted. Otherwise, output "`NO`" (both without quotes).
Sample Input
 
   
3 3 2 1 7 3 3 2 1 5 3 1 4 1 5
Sample Output
 
   
YES YES NO


数据范围比较大,所以不能用双重for循环

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;


#define N 240000
#define INF 0x3f3f3f3f
#define PI acos (-1.0)
#define EPS 1e-8
#define met(a, b) memset (a, b, sizeof (a))

const int dir[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};

typedef long long LL;

int a[N];

int main ()
{
    int t, n;
    scanf ("%d", &t);

    while (t--)
    {
        int flag = 0;

        scanf ("%d", &n);

        for (int i=0; i= a[i-1])
                p++;
            else
            {
                Index = i;
                cnt++;
            }
        }

        if (p == n-1) flag = 1;

        if (cnt == 1)
        {
            if (Index == 1 || Index == n-1 || a[Index-1]<=a[Index+1] || a[Index-2]<=a[Index])
                flag = 1;
        }

        cnt = 0, Index = 1;
        for (int i=1; i=a[Index+1] || a[Index-2]>=a[Index])
                flag = 1;
        }

        if (flag) puts ("YES");
        else puts ("NO");
    }
    return 0;
}


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