60. 746. Min Cost Climbing Stairs

class Solution {
      int arr[]= new int[1001];
    public int minCostClimbingStairs(int[] cost) {
        Arrays.fill(arr, -1);
        return Math.min(solve(cost, 0), solve(cost, 1));
        
    }

    private int solve(int cost[],int index){
        if(index>=cost.length){
            return 0;
        }
        if(arr[index]!= -1){
            return arr[index];
        }
        int a=cost[index]+solve(cost,index+1);
        int b =cost[index]+ solve(cost,index+2);
       return arr[index] = Math.min(a,b);
    }
}