leetcode第59题螺旋矩阵 II

题目： 给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

我的JavaScript解法：

/**
 * @param {number} n
 * @return {number[][]}
 */
var generateMatrix = function(n) {
  let matrix = new Array();
  for(let i = 0; i < n; i++) {
    matrix[i] = new Array(n);
  }
  let upperBound = 0, lowerBound = n -1;
  let leftBound = 0, rightBound = n - 1;
  let number = 1;
  while(number <= n*n) {
    if(upperBound <=lowerBound) {
      for(let i = leftBound; i <= rightBound; i++) {
        matrix[upperBound][i] = number++;
      }
      upperBound++;
    }
    if(leftBound <=rightBound) {
      for(let i = upperBound; i <= lowerBound; i++) {
        matrix[i][rightBound] = number++;
      }
      rightBound--;
    }
    if(upperBound <=lowerBound) {
      for(let i = rightBound; i >= leftBound; i--) {
       matrix[lowerBound][i] = number++;
      }
      lowerBound--;
    }
    if(leftBound <=rightBound) {
      for(let i = lowerBound; i >= upperBound; i--) {
        matrix[i][leftBound] = number++;
      }
      leftBound++;
    }
  }
  return matrix;
};