leetcode第16題（candy）

題目：

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?

思路：

周遊兩邊，首先每個人得一塊糖，第一遍從左到右，若目前點比前一個點高就比前者多一塊。

這樣保證了在一個方向上滿足了要求。第二遍從右往左，若左右兩點，左側高于右側，但

左側的糖果數不多于右側，則左側糖果數等于右側糖果數+1，這就保證了另一個方向上滿足要求

代碼：

import java.util.Arrays;

public class Solution {
    public int candy(int[] ratings) {
        if(ratings == null || ratings.length == 0){
            return 0;
        }
        int n = ratings.length;
        int[] candy = new int[n];
        int sum=0;
        Arrays.fill(candy,1);
        for(int i=1;i<n;i++){
            if(ratings[i]>ratings[i-1]){
                candy[i] = candy[i-1]+1;
            }
        }
        for(int i=n-1;i>=1;i--){
            if(ratings[i-1]>ratings[i] && candy[i-1] <= candy[i]){
                candy[i-1 ] = candy[i]+1;
            }
        }
        for(int num:candy){
            sum+=num;
        }
        return sum;
    }
}