LeetCode: Candy 解题报告

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?

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SOLUTION:

使用一个数组记录每一个小孩应得的糖果的数目

1.我们可以从左往右扫描，如果遇到上升区间，就给小孩比左边多一个糖，否则就给1个糖果。

2.我们可以从右往左扫描，如果遇到上升区间，就给小孩比右边多一个糖，否则就给1个糖果。

同时，应该与1步算出的值取一个大值（因为有可能要给小孩更多糖果才可以满足题设）。

 public class Solution {
     public int candy(int[] ratings) {
         if (ratings == null || ratings.length == ) {
             return ;
         }

         int len = ratings.length;
         int[] num = new int[len];

         // go from left to right;
         for (int i = ; i < len; i++) {
             if (i >  && ratings[i] > ratings[i - ]) {
                 num[i] = num[i - ] + ;
             } else {
                 num[i] = ;
             }
         }

         // go from right to left;
         int sum = ;
         for (int i = len - ; i >= ; i--) {
             if (i < len -  && ratings[i] > ratings[i + ]) {
                 num[i] = Math.max(num[i], num[i + ] + );
             }
             sum += num[i];
         }

         return sum;
     }
 }

CODE:

https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/dp/Candy.java