135. 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?

N个孩子有不同的等级编号，站成一排等着分糖果。

规定每个孩子至少有一个糖果，等级高的孩子比相邻等级低的孩子分到的糖果要多。

举例说明：输入【2，2】，则每人一个糖果，共需2个；输入【1，2，3】则需要6个糖果；【2，3，2】，则需要4个糖果。

使用贪心算法，先正向遍历，等级高的孩子比左相邻的孩子糖果数加1；同理，再反向遍历，则可以形成金子塔型的糖果分布。

class Solution {
public:
int candy(vector<int>& ratings) {
if(ratings[0]==0)
return 1;
int n = ratings.size();
vector<int> temp(n,1); //temp记录每人手里糖果数量，初始为1

for(int i = 1;i<ratings.size();i++) {     //正向遍历
if (ratings[i]>ratings[i-1]&&temp[i]<=temp[i-1]){
temp[i] = temp[i-1]+1;
}
}
for(int i = n-1;i>=0;i--) {    //反向遍历
if (ratings[i-1]>ratings[i]&&temp[i-1]<=temp[i]){
temp[i-1] = temp[i]+1;
}
}
int sum = 0;
for(int i = 0;i<n;i++) {
sum += temp[i];
}
return sum;
}
};