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]
]


C++(3ms):
 1 class Solution {
 2 public:
 3     vector<vector<int>> generate(int numRows) {
 4         vector<vector<int>> res(numRows) ;
 5         if (numRows < 1)
 6             return res ;
 7         for (int i = 0 ; i < numRows ; i++){
 8             res[i].resize(i + 1);
 9             res[i][0] = res[i][i] = 1 ;
10             for (int j = 1 ; j < i ; j++){
11                 res[i][j] = res[i-1][j-1]+res[i-1][j] ;
12                 
13             }             
14         }
15         return res ;
16     }
17 };

 

java(1ms):

 1 class Solution {
 2     public List<List<Integer>> generate(int numRows) {
 3         List<List<Integer>> res = new ArrayList<List<Integer>>() ;
 4         
 5         if (numRows < 1)
 6             return res ;
 7         for(int i = 0 ; i < numRows ; i++){
 8             ArrayList<Integer> row = new ArrayList<Integer>() ;
 9             for(int j = 0 ; j < i + 1; j++){
10                 if (j == 0 || j == i)
11                     row.add(1) ;
12                 else
13                     row.add(res.get(i-1).get(j-1) + res.get(i-1).get(j)) ;
14             }
15             res.add(row) ;
16         }
17         return res ;
18     }
19 }

 

posted @ 2017-09-21 16:11  __Meng  阅读(156)  评论(0)  编辑  收藏  举报