poj3250 Bad Hair Day **

/*
 * DA-term-Bad Hair Day.cpp
 *
 *    这是一种解法，还可以用 “单调队列” 来做(见后。。)
 *
 *  Created on: 2011-12-2
 */

#include <iostream>
using namespace std;

const int maxn = 80000 + 5;

int h[maxn], n;
int num[maxn], cow[maxn];    //num[i]:第i头牛能看到的牛数
//cow[i]:在第i头牛东边第一个比i高的牛

int main(){
    cin >> n;

    for(int i=0; i<n; i++)
        cin >> h[i];

    unsigned long long ans = 0;            //用long long
    int  i, k;
    num[n-1] = 0; cow[n-1] = -1;

    for(i=n-2; i>=0; i--){
        if(h[i] < h[i+1]){
            num[i] = 0; cow[i] = i+1;
        }
        else{
            k = i + 1;
            while(k != -1 && h[k] < h[i]){
                num[i] += (num[k] + 1);
                k = cow[k];
            }
            cow[i] = k;                        //注意更新cow
            ans += num[i];

        }
    }

    //printf("%ld\n", ans);                //printf(“%u”, ans);
    cout << ans << endl;

    return 0;
}

　　

　　

//单调队列法：

　　

#include <iostream>
//#include <cstdio>
using namespace std;

const int maxn = 80 + 5;
const int inf = 1000000000 + 2;

unsigned long long ans = 0;
int h[maxn], monoq[maxn], n;

int main(){
    //scanf("%d", &n);
    cin >> n;

    int tail = -1;
    h[n] = inf;
    for(int i=0; i<n; i++){
        //scanf("%d", &h[i]);
        cin >> h[i];
    }

    for(int i=0; i<=n; i++){
        while(tail >= 0 && h[monoq[tail]] <= h[i]){        //用 <=
            ans += (i - monoq[tail] - 1);
            tail--;
        }
        monoq[++tail] = i;
    }

    //printf("%u\n", ans);
    cout << ans << endl;



    return 0;
}