Diagonal Traverse

Description

Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

 

Example:

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

 

Note:

The total number of elements of the given matrix will not exceed 10,000.

Solution(javascript)

/*
 * @lc app=leetcode id=498 lang=javascript
 *
 * [498] Diagonal Traverse
 */

// @lc code=start
/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
const findDiagonalOrder = function (matrix) {
  const result = []

  let i = 0
  let j = 0
  let up = true
  while (i < matrix.length && j < matrix[i].length) {
    result.push(matrix[i][j])
    if (up) {
      if (j === matrix[i].length - 1) {
        up = false
        i++
      } else if (i === 0) {
        j++
        up = false
      } else {
        i--
        j++
      }
    } else if (i === matrix.length - 1) {
      up = true
      j++
    } else if (j === 0) {
      up = true
      i++
    } else {
      i++
      j--
    }
  }
  return result
}
// @lc code=end