118. Pascal's Triangle

[soonlive]

  /**
   * @param {number} numRows
   * @return {number[][]}
   */
  var generate = function (numRows) {
    var result = [];

    for (var i = 0; i < numRows; ++i) {
      result[i] = [1];
      for (var j = 1; j <= i; ++j) {
        if (j === i) {
          result[i][j] = 1;
        } else {
          if (result[i - 1][j] !== undefined) {
            result[i][j] = result[i - 1][j - 1] + result[i - 1][j];
          }
        }
      }
    }
    return result;
  };