https://leetcode.com/problems/candy/

candy.js

/*
Idea:
1. Find the worst-rated children and start with them
2. For Each worst child, give them just one candy (c)
3. For each neighbour,
  - If they have a higher rating, give them c + 1 candies
  - Otherwise give them 1 candy
4. If ever there is a conflict, round up.

The code ends up being a straightforward breadth-first search. O(n) space and time.
*/

var candy = function(ratings) {
    
    const result = new Array(ratings.length).fill(0);
    const min = Math.min(...ratings, 0);

    const q = [];
    ratings.forEach((r, i) => {
        if(r === min) q.push([i, 1]);
    });
    
    while(q.length){    
        const [index, candies] = q.shift();
        
        if(result[index] < candies) result[index] = candies;
        else continue;
        
        if(index > 0){
            const left = index - 1;
            const leftCandy = ratings[left] > ratings[index] ? (candies+1) : 1;
            if(leftCandy > result[left]) q.push([left, leftCandy]);
        }
        
        if(index < ratings.length-1){
            const right = index + 1;
            const rightCandy = ratings[right] > ratings[index] ? (candies+1) : 1;
            if(rightCandy > result[right]) q.push([right, rightCandy]);
        }
    }
    
    return result.reduce((a, b) => a + b, 0);
};