Pascal's Triangle(也称杨辉三角)

描述

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

Example

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

import java.util.ArrayList;
import java.util.List;

public class PascalTriangle {
    public static void main(String[] args) {
        System.out.println(generate(5));
    }
    public static List<List<Integer>> generate(int numRows) {
        List<List<Integer>> result = new ArrayList<List<Integer>>(numRows);
        for (int i = 0; i < numRows; i++) {
            List<Integer> thisRow = new ArrayList<Integer>(i);
            for (int j = 0; j <= i; j++) {
                if(j==0)
                    thisRow.add(1);
                else{
                    if(j<i)
                        thisRow.add( result.get(i - 1).get(j - 1) + result.get(i - 1).get(j));
                    else if(j==i)
                        thisRow.add(1);
                }
            }
            result.add(thisRow);
        }
        return result;
    }
}