tapping rain water

will add notes after discussion

/** * @param {number[]} height * @return {number} */var trap = function (height) {  let arr = height;  let kadanes = [];  let maxi = arr[0];  kadanes.push(0);  for (let i = 1; i < arr.length; i++) {    maxi = Math.max(maxi, arr[i]);    kadanes.push(maxi - arr[i]);  }  maxi = arr[arr.length - 1];
  for (let i = arr.length - 2; i >= 0; i--) {    maxi = Math.max(maxi, arr[i]);    let right = maxi - arr[i];    kadanes[i] = Math.min(kadanes[i], right);  }  kadanes[arr.length - 1] = 0;
  let sum = 0;  let total = 0;  for (let i = 0; i < kadanes.length; i++) {    sum += kadanes[i];  }
  return sum;  //your code here};