javascript - Can someone explain the rainwater capture two pointer solution to me?

Question

Can someone help me understand how this two pointer solution to the rainwater capture interview problem works exactly? I don't understand the different steps involved and why they work. It would be very helpful if someone could walk me through it step by step.

The actual problem

function twoPointerRainwater(heights) {
  let totalWater = 0;
  let leftPointer = 0;
  let rightPointer = heights.length - 1;
  let leftBound = 0;
  let rightBound = 0;
  
  while (leftPointer < rightPointer) {
    if (heights[leftPointer] <= heights[rightPointer]) {
      leftBound = Math.max(heights[leftPointer], leftBound);
      totalWater += leftBound - heights[leftPointer];
      leftPointer++;
    } else {
      rightBound = Math.max(heights[rightPointer], rightBound);
      totalWater += rightBound - heights[rightPointer];
      rightPointer--;
    }
  }
  return totalWater;
}

Answer 1

等待大神答复