POJ2823 Sliding Window

Description An array of size n ≤ 106 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.

单调队列模板题。

#include<cstdio>#include<cstring>int a[1000010],q[1000010];int main(){    int i,j,k,m,n,p,x,t,z,hd,tl;    scanf("%d%d",&n,&k);    for (i=1;i<=n;i++)      scanf("%d",&a[i]);    q[1]=hd=tl=1;    for (i=1;i<=n;i++)    {        if (i-q[hd]>=k) hd++;        while (hd<=tl&&a[q[tl]]>=a[i]) tl--;        q[++tl]=i;        if (i>=k)        {            printf("%d",a[q[hd]]);            if (i==n) printf("\n");            else printf(" ");        }    }    q[1]=hd=tl=1;    for (i=1;i<=n;i++)    {        if (i-q[hd]>=k) hd++;        while (hd<=tl&&a[q[tl]]<=a[i]) tl--;        q[++tl]=i;        if (i>=k)        {            printf("%d",a[q[hd]]);            if (i==n) printf("\n");            else printf(" ");        }    }}