Method paintWalls

java/2742-painting-the-walls.java:3–7

(int[] cost, int[] time)

class Solution {
    Map<String, Integer> dp;
    public int paintWalls(int[] cost, int[] time) {
        int n = cost.length;
        dp = new HashMap<>();
        return dfs(0, cost.length, cost, time);
    }
    private int dfs(int i, int remain, int[] cost, int[] time){
        if(remain <= 0)
            return 0;