1130. Minimum Cost Tree From Leaf Values

class Solution {
    public int mctFromLeafValues(int[] arr) {
        int result = 0;
        Stack<Integer> stack = new Stack<>();
        stack.push(Integer.MAX_VALUE);

        for (int value : arr) {
            while (stack.peek() <= value) {
                int mid = stack.pop();
                result += mid * Math.min(stack.peek(), value);
            }
            stack.push(value);
        }

        while (stack.size() > 2) {
            result += stack.pop() * stack.peek();
        }

        return result;
    }
}