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http://poj.org/problem?id=3250
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Bad Hair Day
Description Some of Farmer John‘s N cows (1 ≤ N ≤ 80,000) are having a bad hair day! Since each cow is self-conscious about her messy hairstyle, FJ wants to count the number of other cows that can see the top of other cows‘ heads. Each cow i has a specified height hi (1 ≤ hi ≤ 1,000,000,000) and is standing in a line of cows all facing east (to the right in 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 are strictly shorter than cow i. Consider this example: = Cow#1 can see the hairstyle of cows #2, 3, 4 Let ci denote the number of cows whose hairstyle is visible from cow i; please compute the sum 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 that is the height of cow i. Output Line 1: A single integer that is the sum of c1 through cN.
Sample Input 6 10 3 7 4 12 2 Sample Output 5 Source |
#include<stdio.h> #define N 80010 int Stack[N]; int main() { int top = 0, i, n, p; __int64 sum = 0; scanf("%d", &n); for(i=1; i<=n; i++) { scanf("%d", &p); while(top>0 && Stack[top]<=p) top--; sum += top; Stack[++top] = p; } printf("%I64d\n", sum); return 0; }
（单调队列） Bad Hair Day -- POJ -- 3250
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原文地址：http://www.cnblogs.com/YY56/p/4968221.html
