118. Pascal's Triangle

Problem

Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it.

Example:

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

Solution

/**
 * @param {number} numRows
 * @return {number[][]}
 */
var generate = function(numRows) {
  var i = 0;
  var j = 0;
  var res = [];
  for (i = 0; i < numRows; i++) {
    res.push(Array(i + 1));
    for (j = 0; j <= i; j++) {
      if (j === 0 || j === i) {
        res[i][j] = 1;
      } else {
        res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
      }
    }
  }
  return res;
};

Explain:

nope.

Complexity:

• Time complexity : O(n^2).
• Space complexity : O(n^2).