leetcode No135. Candy

Question

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?

小朋友分糖果，要求：

1、每个小朋友至少分一个糖

2、拥有高rate的小朋友分的糖比他相邻的小朋友多

Algorithm

1、前向遍历，如果右比左高，v[i]=v[i-1]+1

2、后向遍历，如果左比右高，v[i]=max(v[i],v[i+1]+1)

如何证明？

Accepted Code

class Solution {
public:
int candy(vector<int>& ratings) {
int n=ratings.size();
int sum=0;
vector<int> v(n,1);
for(int i=1;i<n;i++){
if(ratings[i] > ratings[i-1]){
v[i]=v[i-1]+1;
}
}
sum = v[n-1];
for(int i=n-1;i>0;i--){
if(ratings[i-1]>ratings[i] && v[i-1]<=v[i]){
v[i-1]=v[i]+1;
}
sum += v[i-1];
}

return sum;
}
};