Pascal's-Triangle

发表于 | 分类于

title

image

Wikipedia article on Pascal’s Triangle: http://en.wikipedia.org/wiki/Pascal’s_triangle

example

1
pascalsTriangle(4) == [1,1,1,1,2,1,1,3,3,1]

My solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
function pascalsTriangle(n) {
  //return a flat array representing the values of Pascal's Triangle to the n-th level
  var result = [];
  var partPre = [];
  for(var i = 1;i<=n;i++){
    var part = Array(i).fill(1);
    for(var j = 1;j<i-1;j++){
        part[j] = partPre[j]+partPre[j-1];
    }
    
    partPre = [].concat(part);
    result = result.concat(part);
  }
  return result;
}

good solution

1
2
3
4
5
6
7
8
9
10
11
12
function pascalsTriangle(n) {
  if (n === 1) {
    return [1];
  }
  var prev = pascalsTriangle(n - 1), len = prev.length;
  prev.push(1);
  for (var i = len - n + 1; i < len - 1; i ++) {
    prev.push(prev[i] + prev[i + 1]);
  }
  prev.push(1);
  return prev;
}