Pascal’s Triangle (Easy)

Description

Given numRows, generate the first numRows of Pascal’s triangle.

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Return

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

Analysis

简单递推

My Solution

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//C++
class Solution {

public:
    vector<vector<int> > generate(int numRows) {
        vector<vector<int> >ans;
        for(int i = 0 ;i<numRows;i++){
            ans.push_back(vector<int>(i+1));
            ans[i][0] = 1;
            ans[i][i] = 1;
        }
        for(int i = 2;i<numRows;i++){
            for(int j = 1;j<i;j++){
                ans[i][j] = ans[i-1][j-1]+ans[i-1][j];
            }
        }
        return ans;
    }
};