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p119

admin 11月 12, 2020 0

LeetCode p119 Pascal’s Triangle II 题解

1.题目：

Given an index k, return the kth row of the Pascal’s triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?

题意：

输入一个数K 求杨辉三角形第K列【从0开始

2.解题思路:

见代码

3.代码

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public class  {
    public List<Integer> getRow(int rowIndex) {
        List<Integer> ans = new ArrayList<Integer>();
		ans.add(1);
		for (int i = 1; i <= rowIndex; i++) {
			for (int j = i - 1; j > 0; j--) {

				ans.set(j, ans.get(j) + ans.get(j - 1));

			}
			ans.add(i, 1);
			
		}
		return ans;
    }
}

4.一些总结：