135. Candy（js）

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?

Example 1:

Input: [1,0,2]
Output: 5
Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively.

Example 2:

Input: [1,2,2]
Output: 4
Explanation: You can allocate to the first, second and third child with 1, 2, 1 candies respectively.
             The third child gets 1 candy because it satisfies the above two conditions.
题意：给定一个数组，每个数组项代表一排小朋友的等级，比较相邻小朋友，等级高的比等级低的拿的糖果多。求给出总糖果数量？
代码如下：

/**
 * @param {number[]} ratings
 * @return {number}
 */
var candy = function(ratings) {
//     init
    let candies=new Array(ratings.length).fill(1);
//     from left to right
    for(let i=1;i<ratings.length;i++){
        if(ratings[i]>ratings[i-1]){
            candies[i]=candies[i-1]+1;
        }
    }
//     from right to left
    for(let i=ratings.length-2;i>=0;i--){
        if(candies[i]<=candies[i+1] && ratings[i]>ratings[i+1]){
            candies[i]=candies[i+1]+1;
        }
    }
//     get sum
    return candies.reduce(function(prev,curr){return prev+curr});
};