118

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

Companies: Amazon, Adobe, Google

Related Topics:
Array, Dynamic Programming

Similar Questions:

• Pascal's Triangle II (Easy)

Solution 1.

// OJ: https://leetcode.com/problems/pascals-triangle/
// Author: github.com/lzl124631x
// Time: O(N^2)
// Space: O(1)
class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> ans(numRows);
        for (int i = 0; i < numRows; ++i) {
            ans[i] = vector<int>(i + 1, 1);
            for (int j = 1; j < i; ++j) ans[i][j] = ans[i - 1][j - 1] + ans[i - 1][j];
        }
        return ans;
    }
};