LeetCode in Kotlin

118. Pascal’s Triangle

Easy

Given an integer numRows, return the first numRows of Pascal’s triangle.

In Pascal’s triangle, each number is the sum of the two numbers directly above it as shown:

Example 1:

Input: numRows = 5

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

Example 2:

Input: numRows = 1

Output: [[1]]

Constraints:

• 1 <= numRows <= 30

Solution

class Solution {
    fun generate(numRows: Int): List<List<Int>> {
        val output: MutableList<List<Int>> = ArrayList()
        for (i in 0 until numRows) {
            val currRow: MutableList<Int> = ArrayList()
            for (j in 0..i) {
                if (j == 0 || j == i || i <= 1) {
                    currRow.add(1)
                } else {
                    val currCell = output[i - 1][j - 1] + output[i - 1][j]
                    currRow.add(currCell)
                }
            }
            output.add(currRow)
        }
        return output
    }
}

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