118. Pascal’s Triangle

Description

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

Hints/Notes

• 2025/01/19
• 0x3F’s solution(checked)

Solution

Language: C++

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> c(numRows);
        for (int i = 0; i < numRows; i++) {
            c[i].resize(i + 1, 1);
            for (int j = 1; j < i; j++) {
                // 左上方的数 + 正上方的数
                c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
            }
        }
        return c;
    }
};