2015ACM/ICPC亚洲区长春站-重现赛 1006 Almost Sorted Array

#include<stdio.h>
#include<string.h>
#include<queue>
#include<math.h>
#include<stdlib.h>
#include<algorithm>
using namespace std;

const int N=1e5+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;

typedef long long LL;

int a[N], flag;

void Increase(int n)
{
    int i, num, idex;

    num = flag = 0;

    for (i = 2; i <= n; i++)
    {
        if (a[i] < a[i-1])
        {
            num++;
            idex = i; ///标记不满足元素的下标
        }
    }

    if (num == 0) flag = 1;

    if (num == 1)
    {
        if (idex == n || idex == 2 || a[idex-2] <= a[idex] || a[idex-1] <= a[idex+1])
            flag = 1; ///如果这个不满足元素的左边和右边还是非递减的，那么可以去掉该元素，或者该元素前的第二个元素和该元素是非递减的，可以去掉该元素之前的第一个元素
    }
}

void Decrease(int n)
{
    int idex, i, num;

    num = flag = 0;

    for (i = 2; i <= n; i++)
    {
        if (a[i] > a[i-1])
        {
            num++;
            idex = i;
        }
    }

    if (num == 0) flag = 1;

    if (num == 1)
    {
        if (idex == 2 || idex == n || a[idex-1] >= a[idex+1] || a[idex-2] >= a[idex])
            flag = 1;
    }
}

int main ()
{
    int T, i, n;

    scanf("%d", &T);

    while (T--)
    {
        scanf("%d", &n);
        for (i = 1; i <= n; i++)
            scanf("%d", &a[i]);

        Increase(n); ///先判断是否是非递减序列：找到不满足条件的元素下标，并统计个数，个数<=1时才满足条件
        if (flag == 0) Decrease(n); ///如果不是非递减序列再判断是否是非递增序列

        if (flag == 1) printf("YES\n");
        else printf("NO\n");
    }

    return 0;
}