題目

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.

題意

計算巴斯卡三角形

Example:

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

解題想法

這題的重點在於如何抓到上一個陣列的值，算出現有陣列的值。

Solution

var generate = function (numRows) {
  let a = [];
  let a1 = [1];
  let a3 = [];
  for (let i = 0; i < numRows; i++) {
    a = a1.slice(0);
    if (i !== 0) {
      a1 = [];
    }
    a3.push(a);
    for (let j = 0; j < i + 1; j++) {
      if (j === 0) {
        a1.push(1);
      } else {
        a1.push(a[j - 1] + a[j]);
      }
      if (j === i && i !== 0) {
        a1.push(1);
      }
    }
  }
  return a3;
};