poj-3250 Bad Hair Day **

 1 /*
 2  * DA-term-Bad Hair Day.cpp
 3  *
 4  *    这是一种解法，还可以用 “单调队列” 来做(见后。。)
 5  *
 6  *  Created on: 2011-12-2
 7  */
 8 
 9 #include <iostream>
10 using namespace std;
11 
12 const int maxn = 80000 + 5;
13 
14 int h[maxn], n;
15 int num[maxn], cow[maxn];    //num[i]:第i头牛能看到的牛数
16 //cow[i]:在第i头牛东边第一个比i高的牛
17 
18 int main(){
19     cin >> n;
20 
21     for(int i=0; i<n; i++)
22         cin >> h[i];
23 
24     unsigned long long ans = 0;            //用long long
25     int  i, k;
26     num[n-1] = 0; cow[n-1] = -1;
27 
28     for(i=n-2; i>=0; i--){
29         if(h[i] < h[i+1]){
30             num[i] = 0; cow[i] = i+1;
31         }
32         else{
33             k = i + 1;
34             while(k != -1 && h[k] < h[i]){
35                 num[i] += (num[k] + 1);
36                 k = cow[k];
37             }
38             cow[i] = k;                        //注意更新cow
39             ans += num[i];
40 
41         }
42     }
43 
44     //printf("%ld\n", ans);                //printf(“%u”, ans);
45     cout << ans << endl;
46 
47     return 0;
48 }

　　

　　

//单调队列法：

　　

 1 #include <iostream>
 2 //#include <cstdio>
 3 using namespace std;
 4 
 5 const int maxn = 80 + 5;
 6 const int inf = 1000000000 + 2;
 7 
 8 unsigned long long ans = 0;
 9 int h[maxn], monoq[maxn], n;
10 
11 int main(){
12     //scanf("%d", &n);
13     cin >> n;
14 
15     int tail = -1;
16     h[n] = inf;
17     for(int i=0; i<n; i++){
18         //scanf("%d", &h[i]);
19         cin >> h[i];
20     }
21 
22     for(int i=0; i<=n; i++){
23         while(tail >= 0 && h[monoq[tail]] <= h[i]){        //用 <=
24             ans += (i - monoq[tail] - 1);
25             tail--;
26         }
27         monoq[++tail] = i;
28     }
29 
30     //printf("%u\n", ans);
31     cout << ans << endl;
32 
33 
34 
35     return 0;
36 }