package org.example;

import java.util.Stack;

public class Trap {

class Unit {

int index;

int height;

public Unit(int index,int height) {

this.index = index;

this.height = height;

}

}

public int trap(int[] height) {

if (height.length == 0) {

return 0;

}

Stack<Unit> stack = new Stack<>();

stack.push(new Unit(0, height[0]));

int total = 0;

for (int i = 1; i < height.length; i++) {

if (stack.isEmpty()) {

stack.push(new Unit(i, height[i]));

continue;

}

Unit left = stack.peek();

int currHeight = height[i];

if (currHeight < left.height) {

} else {

int rightIndex = i;

System.out.println("left = " + left.index + ", right = " + rightIndex);

int sum = 0;

for (int j = left.index + 1; j < rightIndex; j++) {

// bug

// sum = sum + height[j] - left.height;

sum = sum + left.height - height[j];

}

total += sum;

stack.pop();

}

}

return total;

}

public static void main(String[] args) {

Trap trapSolver = new Trap();

int[] height = {0,1,0,2,1,0,1,3,2,1,2,1};

int result = trapSolver.trap(height);

System.out.println("Trapped water: " + result);

}

}