118. Pascal's Triangle

Problem

Tags: Array, Dynamic Programming

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

Code

JS

// 118. Pascal's Triangle (11/26/53440)
// Runtime: 64 ms (74.65%) Memory: 38.84 MB (94.11%) 

/**
 * @param {number} numRows
 * @return {number[][]}
 */
var generate = function(numRows) {
    let triangle = [];
    
    for(let row = 0; row < numRows; row++) {
        let store = [1];
        for(let column = 0; column < row - 1; column++) {
            store.push(triangle[row - 1][column] + triangle[row - 1][column + 1]);
        }
        if(row) store.push(1);
        triangle.push(store);
    }
    
    return triangle;
};