POJ_2823 Sliding Window（单调队列）

　　很裸的单调队列问题，不过O(n)的算法写出来5188+ms，超5s了。。。谁能告诉我500+ms的神级代码是什么。。.T_T

My Code:

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 1000005;

struct node {
    int i;
    int num;
}q[N];

int ans[N];
int b[N];

int main() {
    //freopen("data.in", "r", stdin);

    int n, k, i, f, r;
    while(~scanf("%d%d", &n, &k)) {
        getchar();
        for(i = 0; i < n; i++)
            scanf("%d", &b[i]);

        for(f = r = i = 0; i < n; i++) {

            if(f < r && q[f].i <= i - k)     f++;
            while(f < r && q[r-1].num >= b[i])    r--;

            q[r].i = i; q[r].num = b[i]; r++;

            ans[i] = q[f].num;
        }

        for(i = k-1; i < n; i++) {
            printf("%d", ans[i]);
            if(i != n-1)    putchar('');
            else    putchar('\n');
        }

        for(f = r = i = 0; i < n; i++) {

            if(f < r && q[f].i <= i - k)    f++;
            while(f < r && q[r-1].num <= b[i])    r--;

            q[r].i = i; q[r].num = b[i]; r++;

            ans[i] = q[f].num;
        }

        for(i = k-1; i < n; i++) {
            printf("%d", ans[i]);
            if(i != n-1)    putchar('');
            else    putchar('\n');
        }
    }
    return 0;
}