[poj2823]Sliding Window（单调队列）

题意：给定一个序列，求所有滑动窗口内的最值。

解题关键：单调队列裸题，单调递增队列选取最小值，单调递减队列选取最大值。

注意用c++提交，否则会超时。

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#include<iostream>
#include<cmath>
#define maxn 1000005
using namespace std;
typedef long long ll;
int n,k;
int min1[maxn],max1[maxn],pos1[maxn],que1[maxn],a[maxn];
inline int read(){
    char k=0;char ls;ls=getchar();for(;ls<'0'||ls>'9';k=ls,ls=getchar());
    int x=0;for(;ls>='0'&&ls<='9';ls=getchar())x=(x<<3)+(x<<1)+ls-'0';
    if(k=='-')x=0-x;return x;
}
inline void get_min(int n,int k){
    int head=0,rear=0;
    for(int i=1;i<k;i++){
        while(rear>head&&que1[rear-1]>a[i]) rear--;
        que1[rear]=a[i];
        pos1[rear]=i;
        rear++;
    }
    for(int i=k;i<=n;i++){
        while(rear>head&&que1[rear-1]>a[i]) rear--;
        que1[rear]=a[i];
        pos1[rear]=i;
        rear++;
        while(pos1[head]<i-k+1) head++;
        min1[i]=que1[head];
    }
}
inline void get_max(int n,int k){
    int head=0,rear=0;
    for(int i=1;i<k;i++){
        while(rear>head&&que1[rear-1]<a[i]) rear--;
        que1[rear]=a[i];
        pos1[rear]=i;
        rear++;
    }
    for(int i=k;i<=n;i++){
        while(rear>head&&que1[rear-1]<a[i]) rear--;
        que1[rear]=a[i];
        pos1[rear]=i;
        rear++;
        while(pos1[head]<i-k+1) head++;
        max1[i]=que1[head];
    }
}
int main(){
    while(scanf("%d%d",&n,&k)!=EOF){
        for(int i=1;i<=n;i++) a[i]=read();
        get_min(n,k);
        get_max(n,k);
        for(int i=k;i<=n;i++){
            printf("%d%c",min1[i],i==n?'
':' ');
        }
        for(int i=k;i<=n;i++){
            printf("%d%c",max1[i],i==n?'
':' ');
        }
    }
}