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。

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 //#define OPEN_FILE
 5 using namespace std;
 6 const int MAXN = 1000001;
 7 int n, w;
 8 struct  Node{
 9     int v, p;
10 }a[MAXN], d[MAXN];
11 inline bool cmp(int a, int b){
12     if (a < b) return true;
13     if (a > b) return false;
14     return false;
15 }
16 void work(bool flag)
17 {
18     int i, head, tail;
19     memset(d, 0, sizeof(d));
20     head = tail = 1;
21     d[head] = a[1];
22     for (i = 2; i <= w; i++){
23         while (cmp(d[tail].v, a[i].v) == flag){
24             tail--;
25             if (tail < head) break;
26         }
27         d[++tail] = a[i];
28     }
29     printf("%d", d[head]);
30     for (i = w + 1; i <= n; i++){
31         if (head <= tail){
32             while (cmp(d[tail].v, a[i].v) == flag){
33                 tail--;
34                 if (head > tail) break;
35             }
36         }
37         d[++tail] = a[i];
38         while (d[head].p <= i - w){
39             head++;
40         }
41         printf(" %d", d[head]);
42     }
43 }
44
45 int main()
46 {
47 #ifdef OPEN_FILE
48     freopen("in.txt", "r", stdin);
49     freopen("out.txt", "w", stdout);
50 #endif // OPEN_FILE
51     int i;
52     scanf("%d%d", &n, &w);
53     for (i = 1; i <= n; i++){
54         scanf("%d", &a[i].v);
55         a[i].p = i;
56     }
57     work(false);
58     printf("\n");
59     work(true);
60     printf("\n");
61 }