Leetcode 118. Yang Hui Triangle

Leetcode 118. Yang Hui Triangle

Question stem

Given a non-negative integer numRows, generate the first numRows rows of the Yang Hui triangle.
In the Yanghui triangle, each number is the sum of the numbers on its upper left and upper right.

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

answer

Simulation, pay attention to judge the beginning and end of each line

class Solution {
    
    
public:
    vector<vector<int>> generate(int numRows) {
    
    
        vector<vector<int> > yhTri(numRows);
        if(numRows == 0){
    
    
            return yhTri;
        }
        yhTri[0].push_back(1);
        for(int i = 1 ; i < numRows ; ++i){
    
    
            for(int j = 0 ; j < i + 1 ; ++j){
    
    
                yhTri[i].push_back(j == 0 || j == i ? 1 : yhTri[i-1][j-1] + yhTri[i-1][j]);
            }
        }
        return yhTri;
    }
};