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· One min read
Shi Xinyu
Shi Xinyu
Front End Developer

Given a 2D integer array matrix, return the transpose of matrix.

The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix's row and column indices. link: https://leetcode.com/problems/transpose-matrix/

Example

Example 1:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[1,4,7],[2,5,8],[3,6,9]]

Example 2:

Input: matrix = [[1,2,3],[4,5,6]] Output: [[1,4],[2,5],[3,6]]

/**
 * @param {number[][]} matrix
 * @return {number[][]}
 */
var transpose = function (matrix) {
  if (!matrix.length) return;
  const numOfCols = matrix[0].length;
  const numOfRows = matrix.length;
  const result = [];
  for (let i = 0; i < numOfCols; i++) {
    result.push([]);
  }
  for (let i = 0; i < numOfCols; i++) {
    for (let j = 0; j < numOfRows; j++) {
      result[i][j] = matrix[j][i];
    }
  }
  return result;
};

Interestingly enough, [3, 0, -2, -1, 1, 2].sort() gives [ -1, -2, 0, 1, 2, 3 ]

1464. Maximum Product of Two Elements in an Array

· One min read
Shi Xinyu
Shi Xinyu
Front End Developer

Given a 2D integer array matrix, return the transpose of matrix.

Given the array of integers nums, you will choose two different indices i and j of that array. Return the maximum value of (nums[i]-1)*(nums[j]-1).

Example

Example 1:

Input: nums = [3,4,5,2] Output: 12 Explanation: If you choose the indices i=1 and j=2 (indexed from 0), you will get the maximum value, that is, (nums[1]-1)(nums[2]-1) = (4-1)(5-1) = 3*4 = 12. Example 2:

Input: nums = [1,5,4,5] Output: 16 Explanation: Choosing the indices i=1 and j=3 (indexed from 0), you will get the maximum value of (5-1)*(5-1) = 16. Example 3:

Input: nums = [3,7] Output: 12

/**
 * @param {number[]} nums
 * @return {number}
 */
var maxProduct = function (nums) {
  nums.sort((a, b) => a - b);
  const len = nums.length;
  return (nums[len - 1] - 1) * (nums[len - 2] - 1);
};

867. Transpose Matrix

· One min read
Shi Xinyu
Shi Xinyu
Front End Developer

Given a 2D integer array matrix, return the transpose of matrix.

The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix's row and column indices. link: https://leetcode.com/problems/transpose-matrix/

Example

Example 1:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[1,4,7],[2,5,8],[3,6,9]]

Example 2:

Input: matrix = [[1,2,3],[4,5,6]] Output: [[1,4],[2,5],[3,6]]

/**
 * @param {number[][]} matrix
 * @return {number[][]}
 */
var transpose = function (matrix) {
  if (!matrix.length) return;
  const numOfCols = matrix[0].length;
  const numOfRows = matrix.length;
  const result = [];
  for (let i = 0; i < numOfCols; i++) {
    result.push([]);
  }
  for (let i = 0; i < numOfCols; i++) {
    for (let j = 0; j < numOfRows; j++) {
      result[i][j] = matrix[j][i];
    }
  }
  return result;
};