Leetcode: 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]]

杨辉三角，周末了，来点轻松的。

class Solution {public:    vector<vector<int> > generate(int numRows) {        vector<vector<int> > result;        vector<int> v, last;        for (int i = 0; i < numRows; ++i) {            v.clear();            for (int j = 0; j <= i; ++j) {                if (j == 0 || j == i) {                    v.push_back(1);                }                else {                    v.push_back(last[j-1] + last[j]);                }            }            result.push_back(v);            last = v;        }                return result;    }};

====================第二次======================

class Solution {public:    vector<vector<int> > generate(int numRows) {        vector<vector<int>> result;        vector<int> row;        for (int i = 0; i < numRows; ++i) {            row.resize(i+1);            for (int j = i; j >= 0; --j) {                if (j == 0 || j == i) {                    row[j] = 1;                }                else {                    row[j] += row[j-1];                }            }            result.push_back(row);        }                return result;    }};