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 = ;
 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, , sizeof(d));
     head = tail = ;
     d[head] = a[];
     for (i = ; 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 + ; 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 = ; i <= n; i++){
         scanf("%d", &a[i].v);
         a[i].p = i;
     }
     work(false);
     printf("\n");
     work(true);
     printf("\n");
 }