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]
]
Solution
根据题意进行累加
Complexity
时间复杂度 O(n2 ),空间复杂度 O(n2 )
Code
public class Solution {
public List<List<Integer>> generate(int numRows) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
if (numRows < 1) return res;
List<Integer> temp = new ArrayList<Integer>();
temp.add(1);
res.add(temp);
for (int i = 1; i < numRows; ++i) {
List<Integer> t = new ArrayList<Integer>();
t.add(1);
for (int j = 1; j < i; ++j) {
t.add(res.get(i-1).get(j-1) + res.get(i-1).get(j));
}
t.add(1);
res.add(t);
}
return res;
}
}