135. Candy

题目分析

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?

可以用贪心算法来解出这道题目。

代码

public class Solution {
    public int candy(int[] ratings) {
        if(ratings == null || ratings.length == 0) {
            return 0;
        } 
        if(ratings.length == 1) {
            return 1;
        }
        int sum = 0;
        int[] candys = new int[ratings.length];
        // 第一个孩子先只分一块糖
        candys[0] = 1;
        for(int i = 1; i < ratings.length; i++) {
            // 如果当前的孩子的等级的比左边的高
            if(ratings[i] > ratings[i - 1]) {
                // 右边的孩子的糖果数比左边的多一
                candys[i] = candys[i - 1] + 1;
            } else {
                candys[i] = 1;
            }
        }
        sum += candys[candys.length - 1];
        for(int i = ratings.length - 2; i >= 0; i--) {
            // 如果当前孩子的等级比右边的孩子高
            if(ratings[i] > ratings[i + 1]) {
                candys[i] = Math.max(candys[i], candys[i + 1] + 1);
            }
            sum += candys[i];
        }
        return sum;
    }
}