POJ 3250 Bad Hair Day

Bad Hair Day

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 17727		Accepted: 5981

Description

Some of Farmer John ' S  N  cows (1≤  N  ≤ 80,000) is has a bad hair day! Since Each cow was self-conscious about she messy hairstyle, FJ wants to count the number of other cows so can see the to P of other cows ' heads.

Each cow i have a specified height hi (1≤ hi ≤1,000,000,000) and is standing in a line of cows all facing east (to the right on our diagrams). Therefore, cow I can see the tops of the heads of cows in front of her (namely cows I+ 1, i+2, and so on), for as long as these cows is strictly shorter than cow I.

Consider this example:

=
=       =
=-= Cows facing right---
=   =   =
= - = = =
= = = = = =

Cow#1 can see the hairstyle of cows #2, 3, 4
Cow#2 can see no Cow ' s hairstyle
Cow#3 can see the hairstyle of Cow #4
Cow#4 can see no Cow ' s hairstyle
Cow#5 can see the hairstyle of Cow 6
Cow#6 can see no cows at all!

Let ci denote the number of cows whose hairstyle are visible from cow i; Um of C1 through CN. For this example, the desired is answer 3 + 0 + 1 + 0 + 1 + 0 = 5.

Input

Line 1:the number of cows, N.
Lines 2..n+1:line i+1 contains a single integer so is the height of the cow I.

Output

Line 1: A single integer which is the sum of C1 through cN.

Sample Input

610374122

Sample Output

5

Source

Usaco 2006 November Silverso the cows are facing to the right, ox I can see the cow J when and only when i<j,h[I] > h[k], k=i, I+1, ..., J. maintenance of a monotonic stack, from left to right scan h[i], (1) when the stack is empty, the h[i] pressed into the stack, (2) when the stack is not empty, constantly pop up the top of the stack element, know the current h[i] is less than the top element of the stack, the h[i] press into the stack. In this way, h[i] is pressed into the stack before the stack size, is able to see the number of cows I cattle, the sum can be accumulated.

1#include <iostream>2#include <algorithm>3#include <map>4#include <vector>5#include <functional>6#include <string>7#include <cstring>8#include <queue>9#include <stack>Ten#include <Set> One#include <cmath> A#include <cstdio> - using namespacestd; - #defineIOS Ios_base::sync_with_stdio (False) thetypedefLong LongLL; - Const intINF =0x3f3f3f3f; - Const DoublePi=4.0*atan (1.0); -  + Const intmaxn=80000; - LL ans; + intn,h; A intMain () at { -      while(SCANF ("%d", &n)! =EOF) { -stack<int>s; -ans=0; -          for(intI=0; i<n;i++){ -scanf"%d",&h); in              while(!s.empty () &&h>=s.top ()) S.pop (); -ans+=s.size (); to S.push (h); +         } -printf"%lld\n", ans); the     } *}

POJ 3250 Bad Hair Day