A

http://poj.org/problem?id=2823// 原题链接

题目大意，就是输出每个相邻 (i,i+k+1)区间中的最大值

/// 单调队列练习

#include <algorithm>
#include <stack>
#include <istream>
#include <stdio.h>
#include <map>
#include <math.h>
#include <vector>
#include <iostream>
#include <queue>
#include <string.h>
#include <set>
#include <cstdio>
#define FR(i,n) for(int i=0;i<n;i++)
#define MAX 2005
#define mkp pair <int,int>
using namespace std;
#pragma comment(linker, "/STACK:10240000000,10240000000")
const int maxn = 1e6+5;
typedef long long ll;
const int  inf = 0x3fffff;
void read(int  &x) {
    char ch; bool flag = 0;
    for (ch = getchar(); !isdigit(ch) && ((flag |= (ch == '-')) || 1); ch = getchar());
    for (x = 0; isdigit(ch); x = (x << 1) + (x << 3) + ch - 48, ch = getchar());
    x *= 1 - 2 * flag;
}
int val[maxn];
int Min[maxn],Max[maxn];
int id[maxn],path[maxn];
int main() {
 int n,m;
    while(~scanf("%d%d",&n,&m)){
        vector <int> r1;
        vector <int> r2;
        for(int i=0;i<n;i++)read(val[i]);
        int tail = 1, ed = 0;
        int head = 1, sd = 0;
        for(int i=0;i<m-1;i++){
            while(val[i]<=Min[ed]&&tail<=ed){
                --ed;
            }

            while(val[i]>=Max[sd]&&head<=sd){
                --sd;
            }
            path[++sd]=i;
            Max[sd]=val[i];

            id[++ed]=i;
            Min[ed]=val[i];

        }
    //    r2.push_back(Max[head]);
     //   r1.push_back(Min[tail]);
        for(int i=m-1;i<n;i++){
           //for(int j=tail;j<=ed;j++)printf("%d ",Min[j]);
          // puts("");
            while(val[i]<=Min[ed]&&tail<=ed){
                ed--;
            }


            while(val[i]>=Max[sd]&&head<=sd){
                sd--;
            }

            path[++sd]=i;
            Max[sd]=val[i];
            while(i-path[head]+1>m)head++;
            r2.push_back(Max[head]);

            id[++ed]=i;
            Min[ed]=val[i];
            while(i-id[tail]+1>m)
            {
                tail++;
            }
            r1.push_back(Min[tail]);
        }
        int siz = r1.size();
        for(int i=0;i<siz;i++){
            printf("%d%c",r1[i],(i==(siz-1)?'
':' '));
        }
        for(int i=0;i<siz;i++){
            printf("%d%c",r2[i],(i==(siz-1)?'
':' '));
        }
    }
    return 0;
}