Code Review (Easy): The Dashboard Puddle Problem

Story

While designing a new layout for the internal portal, Lena Sato realized that the varying heights of the data widgets created deep valleys across the interface. Eva Harrington suggested adding a clever weather effect where virtual rain fills these gaps, and she asked Lena to write a utility to calculate exactly how much water would be trapped between the blocks. For example, if a row of widgets had heights like 4, 2, 0, 3, 2, and 5, the tool should determine that the dips would hold a total of 9 units of water. Mark Patel is waiting for this logic so he can finalize the animation for the next team update.

Your Task

Read the story and code, then decide if the code is ready for production or needs improvement.

Hints

What would block an approval? Give me a hint.

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export function trap(height: number[]): number {
  function lengthOf(arr: any[]): number {
    let i = 0;
    while (i in arr) {
      i++;
    }
    return i;
  }

function makeArray(len: number, value: number): number[] {
    const out: number[] = [];
    for (let i = 0; i < len; i++) {
      out[i] = value;
    }
    return out;
  }

function myMax(a: number, b: number): number {
    if (a >= b) return a;
    return b;
  }

function myMin(a: number, b: number): number {
    if (a <= b) return a;
    return b;
  }

const n = lengthOf(height);
  if (n <= 2) return 0;

const leftMax = makeArray(n, 0);
  leftMax[0] = height[0];
  for (let i = 1; i < n; i++) {
    leftMax[i] = myMax(leftMax[i - 1], height[i]);
  }

const rightMax = makeArray(n, 0);
  rightMax[n - 1] = height[n - 1];
  for (let i = n - 2; i >= 0; i--) {
    rightMax[i] = myMax(rightMax[i + 1], height[i]);
  }

let trapped = 0;
  for (let i = 0; i < n; i++) {
    const fill = myMin(leftMax[i], rightMax[i]);
    if (fill > height[i]) {
      trapped += fill - height[i];
    }
  }

return trapped;
}