[LeetCode-118] Pascal's Triangle

Pascal's Triangle

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

For example, given numRows = 5,
Return

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

 

没啥好说的。。。

 

class Solution {
public:
    vector<vector<int> > generate(int numRows) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (0 == numRows) {
            vector<vector<int> > empty_result;
            return empty_result;
        }
        vector<vector<int> > result(1, vector<int>(1, 1));
        for (int i = 1; i < numRows; ++i) {
            vector<int> cur_row;
            const vector<int>& last_row = result[i - 1];
            for (int j = 0; j <= i; ++j) {
                cur_row.push_back((0 == j ? 0 : last_row[j - 1])
                        + (i == j ? 0 : last_row[j]));
            }
            result.push_back(cur_row);
        }
        return result;
    }
};