No.118 Pascal's Triangle

No.118 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]
]

解法：其实很简单，想清楚就好，找好规律！！

 1 #include "stdafx.h"
 2 #include <string>
 3 #include <vector>
 4 #include <iostream>
 5 #include <algorithm>
 6 using namespace std;
 7
 8 class Solution
 9 {
10 public:
11     vector<vector<int>> generate(int numRows)
12     {//生成帕斯卡三角形
13      //找规律
14         vector<vector<int>> res;
15         if(numRows<=0)
16             return res;
17         vector<int> front;
18         for(int i=0; i<numRows; i++)
19         {
20             vector<int> tmp;
21             for(int j=0; j<i+1; j++)
22             {
23                 if(j==0 || j==i)
24                     tmp.push_back(1);
25                 else
26                 {
27                     tmp.push_back(front[j]+front[j-1]);//又是i、j傻傻分不清楚!!!
28                 }
29             }
30             front = tmp;
31             res.push_back(tmp);
32         }
33         return res;
34     }
35 };
36
37 int main()
38 {
39     Solution sol;
40     int numRows;
41     vector<vector<int>> res;
42     while(cin >> numRows)
43     {
44         cout << numRows<<" : "<<endl;
45         res = sol.generate(numRows);
46         for(const auto &i : res)
47         {
48             for(const auto &j : i)
49                 cout << j << " ";
50             cout << endl;
51         }
52         cout <<"--------------"<<endl;
53     }
54 }

No.118 Pascal's Triangle