[LeetCode]118. Pascal’s Triangle

题目描述

思路

水题，根据前数组计算当前数组

代码

#include <iostream>
#include <vector>

using namespace std;

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        /*
        vector<vector<int>> res;
        for (int i = 0; i < numRows; ++i) {
            vector<int> temp;
            if (i < 2)
                for (int j = 0; j <= i; ++j) 
                    temp.push_back(1);
            else {
                int left = 0, right = 1;
                for (int j = 0; j <= i; ++j) {
                    if (j == 0 || j == i)
                        temp.push_back(1);
                    else
                        temp.push_back(res[i - 1][left++] + res[i - 1][right++]);
                }
            }
            res.push_back(temp);
        }
        return res;
        */
        vector<vector<int>> res(numRows);
        for (int i = 0; i < numRows; ++i) {
            res[i].resize(i + 1);
            res[i][0] = 1;
            res[i][i] = 1;

            for (int j = 1; j < i; ++j) {
                res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
            }
        }
        return res;
    }
};

int main() {
    vector<vector<int>> res;
    Solution s;
    res = s.generate(5);

    for (auto vec : res) {
        for (int num : vec)
            cout << num << " ";
        cout << endl;
    }

    system("pause");
    return 0;
}