[LeetCode]118. Pascal's Triangle

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Total Accepted: 77202 Total Submissions: 235367 Difficulty: Easy

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]]

思路：动态规划，根据上一层的结果对这一层进行操作，注意边界值的操作

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

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