LintCode_412 Candy

There are N children standing in a line. Each child is assigned a rating value.

You are giving candies to these children subjected to the following requirements:

• Each child must have at least one candy.

• Children with a higher rating get more candies than their neighbors.

What is the minimum candies you must give?

Have you met this question in a real interview? 

Yes

Example

Given ratings = [1, 2], return 3.

Given ratings = [1, 1, 1], return 3.

Given ratings = [1, 2, 2], return 4. ([1,2,1]).

分析：其实题目描述的有点问题，不是评级越高的小孩可以得到更多的糖果，从第三个样例中可以看出来，应该是“相邻两人里评级高的，可以得到更多的糖果”，一开始可以假设每个小孩都1颗糖果，如果第i个小孩比i-1个小孩rating高，那么糖果数也得比他高，和i+1个小孩比也是这样，于是可以从前往后扫描一遍，再从后往前扫描一遍。

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 print?

1. class Solution {    
2. public:    
3.             
4.     int candy(vector<int>& ratings) {    
5.                 
6.         vector<int> dp(ratings.size(),1);    
7.         for(int i=0;i<ratings.size()-1;i++)    
8.             if(ratings[i]<ratings[i+1])    
9.                 dp[i+1] = max(dp[i+1],dp[i]+1);    
10.                
11.         for(int i=ratings.size()-1;i>=1;i--)    
12.             if(ratings[i]<ratings[i-1])    
13.                 dp[i-1] = max(dp[i-1],dp[i]+1);    
14.                 
15.         return accumulate(dp.begin(),dp.end(),0);    
16.     }    
17. };