leetcode-118 杨辉三角

/**
 * @param {number} numRows
 * @return {number[][]}
 */
var generate = function (numRows) {
  let result = [[1], [1, 1]];
  let pre = [1, 1],
    cur = [];
  if (numRows === 1) return [[1]];
  if (numRows === 2) return [[1], [1, 1]];
  for (let i = 0; i < numRows - 2; ++i) {
    // const sum = (pre[i - 1] || 0) + pre[i];
    for (let i = 0; i < pre.length + 1; i++) {
      cur[i] = (pre[i - 1] || 0) + (pre[i] || 0);
    }
    pre = cur;
    cur = [];
    result.push(pre);
  }
  return result;
};
// console.log(generate(5));

/**
 * @param {number} numRows
 * @return {number[][]}
 */
var generate = function (numRows) {
  let result = [];
  for (let i = 0; i < numRows; i++) {
    const cur = Array(i + 1).fill(1);
    for (let j = 1; j < cur.length - 1; j++) {
      // 模拟过程
      cur[j] = result[i - 1][j - 1] + result[i - 1][j];
    }
    result.push(cur);
  }
  return result;
};
console.log(generate(5));