LeetCode 118 Pascal's Triangle

题目描述

代码

[code]    public List<List<Integer>> generate(int numRows) {

        ArrayList<List<Integer>> rt = new ArrayList<List<Integer>>();

        Integer[] pre = null;

        for (int i = 1; i <= numRows; i++) {

            //must be defined as Integer[]
            Integer[] row = new Integer[i];

            row[0] = 1;
            row[i - 1] = 1;

            for (int j = 1; j < i - 1; j++) {
                row[j] = pre[j] + pre[j - 1];
            }

            rt.add(new ArrayList<Integer>(Arrays.asList(row)));
            pre = row;
        }

        return rt;
    }