Pascal’s Triangle

描述

Given numRows, generate the first numRows of Pascal's triangle.


For example, given numRows = 5,
Return
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

题解

package algorithms

func generate(numRows int) [][]int {
	res := [][]int{}
	if numRows == 0 {
		return res
	}

	res = append(res, []int{1})
	if numRows == 1 {
		return res
	}

	for i := 1; i < numRows; i++ {
		res = append(res, helper(res[i-1]))
	}

	return res
}

func helper(p []int) []int {
	res := make([]int, 1, len(p)+1)
	res = append(res, p...)

	for i := 0; i < len(res)-1; i++ {
		res[i] += res[i+1]
	}

	return res
}