POJ2823(Sliding Window)

题目链接

经典单调队列题。

#include <stdio.h>
#define N 1000005
int a[N];
int q[N],front,rear;
int main()
{
    int i,n,k;
    while(~scanf("%d%d",&n,&k))
    {
        for(i=0;i<n;i++)    scanf("%d",&a[i]);
        front=rear=0;
        for(i=0;i<n;i++)
        {
            while(front<rear&&a[i]<=a[q[rear-1]])  rear--;
            q[rear++]=i;
            while(i-q[front]+1>k)   front++;
            if(i==k-1)    printf("%d",a[q[front]]);
            else if(i>k-1)    printf(" %d",a[q[front]]);
        }
        printf("\n");
        front=rear=0;
        for(i=0;i<n;i++)
        {
            while(front<rear&&a[i]>=a[q[rear-1]])  rear--;
            q[rear++]=i;
            while(i-q[front]+1>k)   front++;
            if(i==k-1)    printf("%d",a[q[front]]);
            else if(i>k-1)    printf(" %d",a[q[front]]);
        }
        printf("\n");
    }
    return 0;
}