POJ2823 单调队列

POJ2823 http://poj.org/problem?id=2823

最基础的单调队列，说是数据结构，其实就是一种更新数组数据的方法。

之前还准备用deque，超时了，直接head,tail快得多。

一直把删除队首过期元素写在删除队尾之前，就一直WA，尼玛换一下顺序就好了。

#include <iostream>
#include <cstdio>
#include <cstring>
//#define OPEN_FILE
using namespace std;
const int MAXN = 1000001;
int n, w;
struct  Node{
    int v, p;
}a[MAXN], d[MAXN];
inline bool cmp(int a, int b){
    if (a < b) return true;
    if (a > b) return false;
    return false;
}
void work(bool flag)
{
    int i, head, tail;
    memset(d, 0, sizeof(d));
    head = tail = 1;
    d[head] = a[1];
    for (i = 2; i <= w; i++){
        while (cmp(d[tail].v, a[i].v) == flag){
            tail--;
            if (tail < head) break;
        }
        d[++tail] = a[i];
    }
    printf("%d", d[head]);
    for (i = w + 1; i <= n; i++){
        if (head <= tail){
            while (cmp(d[tail].v, a[i].v) == flag){
                tail--;
                if (head > tail) break;
            }
        }
        d[++tail] = a[i];
        while (d[head].p <= i - w){
            head++;
        }
        printf(" %d", d[head]);
    }
}

int main()
{
#ifdef OPEN_FILE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif // OPEN_FILE
    int i;
    scanf("%d%d", &n, &w);
    for (i = 1; i <= n; i++){
        scanf("%d", &a[i].v);
        a[i].p = i;
    }
    work(false);
    printf("
");
    work(true);
    printf("
");
}