力扣118、杨辉三角

class Solution {
public:
    vector> generate(int numRows) {
        vector> ans(numRows); //初始化ans的行数
        for (int i = 0; i < numRows; i++) {
            ans[i].resize(i + 1); //初始化该行的列数
            ans[i][0] = ans[i][i] = 1;
            for (int j = 1; j < i; j++) {
                ans[i][j] = (ans[i - 1][j] + ans[i - 1][j - 1]);
            }
        }
        return ans;
    }
};

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