Java DP solution with O(1) space

  • 1
    public class Solution {
    public int minimumTotal(List<List<Integer>> triangle) {
        if(triangle.size() == 0) return 0;
        int size = triangle.size();
        for(int i = 1; i<size; i++){
            int i0 = triangle.get(i).get(0) + triangle.get(i-1).get(0);
            triangle.get(i).set(0, i0);
            int ilast = triangle.get(i).get(i) + triangle.get(i-1).get(i-1);
            for(int j = 1; j<i; j++){
                int sum = triangle.get(i).get(j) + Math.min(triangle.get(i-1).get(j-1), triangle.get(i-1).get(j));
        //get the min of last level nodes
        int min = Integer.MAX_VALUE;
        for(int i = 0; i<size; i++){
            int a = triangle.get(size-1).get(i);
            min = Math.min(a, min);
        return min;

  • 0

    I did the exact same thing. It's cheating though since we modified the input list which may not be allowed in an interview setting.

  • 0

    why not? Interviewers are not robots, they just want to know how you solve the problem.

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