POJ 2823单调队列 数组写法

Sliding Window

Time Limit: 12000MS		Memory Limit: 65536K
Total Submissions: 46443		Accepted: 13422
Case Time Limit: 5000MS

Description

An array of size  n ≤ 10 ⁶ is given to you. There is a sliding window of size  k which is moving from the very left of the array to the very right. You can only see the  k numbers in the window. Each time the sliding window moves rightwards by one position. Following is an example: 
The array is  [1 3 -1 -3 5 3 6 7], and  k is 3.

Window position	Minimum value	Maximum value
[1  3  -1] -3  5  3  6  7	-1	3
1 [3  -1  -3] 5  3  6  7	-3	3
1  3 [-1  -3  5] 3  6  7	-3	5
1  3  -1 [-3  5  3] 6  7	-3	5
1  3  -1  -3 [5  3  6] 7	3	6
1  3  -1  -3  5 [3  6  7]	3	7

Your task is to determine the maximum and minimum values in the sliding window at each position. 

Input

The input consists of two lines. The first line contains two integers  n and  k which are the lengths of the array and the sliding window. There are  n integers in the second line. 

Output

There are two lines in the output. The first line gives the minimum values in the window at each position, from left to right, respectively. The second line gives the maximum values. 

Sample Input

8 3
1 3 -1 -3 5 3 6 7

Sample Output

-1 -3 -3 -3 3 3
3 3 5 5 6 7

Source

POJ Monthly--2006.04.28, Ikki

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;
#define maxn 1000000 + 10
int a[maxn];
int Q[maxn];
int p[maxn];
int Min[maxn];
int Max[maxn];

int n, k;

void get_min()
{
    int head = 1, tail = 0;//初始条件 队列为空
    for(int i=1; i<k; i++)
    {
        while(head <= tail && Q[tail] >= a[i])//进队维护条件
            tail--;
        Q[++tail] = a[i];
        p[tail] = i;
    }
    for(int i=k; i<=n; i++)
    {
        while(head <= tail && Q[tail] >= a[i])
            tail--;
        Q[++tail] = a[i];
        p[tail] = i;
        while(p[head] < i-k+1)
            head++;
        Min[i] = Q[head];
    }
}

void get_max()
{
    int head = 1, tail = 0;
    for(int i=1; i<k; i++)
    {
        while(head <= tail && Q[tail] <= a[i]) tail--;
        Q[++tail] = a[i];
        p[tail] = i;
    }
    for(int i=k; i<=n; i++)
    {
        while(head <= tail && Q[tail] <= a[i]) tail--;
        Q[++tail] = a[i];
        p[tail] = i;
        while(p[head] < i-k+1)
            head++;
        Max[i] = Q[head];
    }
}


int main()
{
    while(~scanf("%d%d", &n, &k))
    {
        for(int i=1; i<=n; i++)
            scanf("%d", &a[i]);

        get_min();
        for(int i=k; i<=n; i++)
            i==n ? printf("%d\n", Min[i]) : printf("%d ", Min[i]);

        get_max();
        for(int i=k; i<=n; i++)
            i==n ? printf("%d\n", Max[i]) : printf("%d ", Max[i]);
    }
    return 0;
}