Pascal's Triangle

return tmpLarge.push_back(tmp);

不等价于

tmpLarge.push_back(tmp);
return tmpLarge;

因为push_back()返回值类型为void,而后者返回tmpLarge的类型。

代码如下：

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        if(numRows == 0) {
            vector<vector<int>> tmpLarge;
            return tmpLarge;
        }
        if(numRows == 1) {
            vector<int> tmp;
            vector<vector<int>> tmpLarge;
            tmp.push_back(1);
            //"return tmpLarge.push_back(tmp);" is error
            tmpLarge.push_back(tmp);
            return tmpLarge;
        }

        vector<vector<int> > smallResult = generate(numRows - 1);
        vector<int> tmp;
        smallResult.push_back(tmp);
        smallResult[numRows - 1].push_back(1);

        for(int i = 0; i <= numRows - 3; i++) {
            smallResult[numRows - 1].push_back(smallResult[numRows - 2][i] + smallResult[numRows - 2][i + 1]);
        }
        smallResult[numRows - 1].push_back(1);

        return smallResult;
    }
};