118PascalTriangle.md

Pascal's Triangle

Description

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.

Example:

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

Tags: Array

思路

题意是给出行数，输出帕斯卡尔三角形，很简单的模拟，就不多说了。

class Solution {
    func generate(_ numRows: Int) -> [[Int]] {
        var list = [[Int]]()
    
        if numRows < 1 {
            return list
        }
        for i in 0..<numRows {
            var subList = [Int]()
            for j in 0...i {
                if j == 0 || j == i {
                    subList.append(1)
                    continue
                }

                let preList = list[i - 1]
                subList.append(preList[j - 1] + preList[j])
            }

            list.append(subList)
        }

        return list
    }
}

结语

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