题目描述:

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

For example, given numRows = 5, Return

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

Pascal三角形就是每一行除了开头和结尾的数是1, 其他数都等于它的左上方与右上方的数之和.

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class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> result(numRows, vector<int>());

        for(int i = 0; i < numRows; i++){
            for(int j = 0; j <= i; j++){
                if(j == 0 || j == i) result[i].push_back(1);
                else{
                    result[i].push_back(result[i - 1][j - 1] + result[i - 1][j]);
                }
            }
        }
        return result;
    }
};