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] ]
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思路上没什么需要说的。需要注意的是ArrayList的使用。
public class Solution { public List<List<Integer>> generate(int numRows) { List<List<Integer>> res = new ArrayList<List<Integer>>(); List<Integer> pre = new ArrayList<Integer>(); if (numRows <= 0) return res; else{ pre.add(1); res.add(pre); } for(int i = 1; i < numRows; i++){ List<Integer> curr = new ArrayList<Integer>(); curr.add(1); for(int j = 0; j < pre.size()-1; j++){ curr.add(pre.get(j) + pre.get(j+1)); } curr.add(1); res.add(curr); pre = curr; } return res; } }