LeetCode [118] Pascal's Triangle

 118. Pascal's Triangle

Easy

Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it.

Example:

Input: 5
Output:
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

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class Solution { public: vector<vector<int>> generate(int numRows) { vector<vector<int>> ret; for(int i=1; i<=numRows; ++i){ vector<int> row(i); for(int j=1; j<=i; ++j){ if(j==1 || j==i) row[j-1] = 1; else row[j-1] = ret.back()[j-2]+ret.back()[j-1]; } ret.push_back(row); } return ret; } };

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class Solution { public List<List<Integer>> generate(int numRows) { List<List<Integer>> lists = new ArrayList<>(); for(int i=0; i<numRows; ++i){ List<Integer> list = new ArrayList<>(); list.add(1); for(int j=1; j<i; ++j){ list.add(lists.get(i-1).get(j-1)+lists.get(i-1).get(j)); } if(i>0) list.add(1); lists.add(list); } return lists; } }