(Leet Code c++)Pascal's Triangle

118. Pascal's Triangle

 

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

파스칼의 삼각형을 DP로 구현.

 

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> answer;
        
        for(int i = 1; i <= numRows; i++){
            vector<int> v(i, 1);
            
            for(int j = 1; j < v.size() - 1; j++){
                v[j] = answer[i - 2][j - 1] + answer[i - 2][j];
            }
            
            answer.push_back(v);
        }
        
        return answer;
    }
};