#3391 - Design a 3D Binary Matrix with Efficient Layer Tracking

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Array Hash Table Matrix Heap Priority Queue Design Ordered Set

Problem Description

You are given a n x n x n binary 3D array matrix.

Implement the Matrix3D class:

Matrix3D(int n) Initializes the object with the 3D binary array matrix, where all elements are initially set to 0.
void setCell(int x, int y, int z) Sets the value at matrix[x][y][z] to 1.
void unsetCell(int x, int y, int z) Sets the value at matrix[x][y][z] to 0.
int largestMatrix() Returns the index x where matrix[x] contains the most number of 1's. If there are multiple such indices, return the largest x.

Solution

/**
 * @param {number} n
 */
var Matrix3D = function(n) {
  this.n = n;
  this.matrix = new Set();
  this.layerCounts = new Array(n).fill(0);
};

/**
 * @param {number} x
 * @param {number} y
 * @param {number} z
 * @return {void}
 */
Matrix3D.prototype.setCell = function(x, y, z) {
  const key = `${x},${y},${z}`;
  if (!this.matrix.has(key)) {
    this.matrix.add(key);
    this.layerCounts[x]++;
  }
};

/**
 * @param {number} x
 * @param {number} y
 * @param {number} z
 * @return {void}
 */
Matrix3D.prototype.unsetCell = function(x, y, z) {
  const key = `${x},${y},${z}`;
  if (this.matrix.has(key)) {
    this.matrix.delete(key);
    this.layerCounts[x]--;
  }
};

/**
 * @return {number}
 */
Matrix3D.prototype.largestMatrix = function() {
  const maxCount = Math.max(...this.layerCounts);
  for (let i = this.n - 1; i >= 0; i--) {
    if (this.layerCounts[i] === maxCount) {
      return i;
    }
  }
  return this.n - 1;
};