2017-10-11 15:11:53 +0000   |     algorithm leetcode array   |   Viewed times   |    

题目

Given a nested list of integers, return the sum of all integers in the list weighted by their depth.

Each element is either an integer, or a list – whose elements may also be integers or other lists.

Example 1: Given the list [[1,1],2,[1,1]], return 10. (four 1’s at depth 2, one 2 at depth 1)

Example 2: Given the list [1,[4,[6]]], return 27. (one 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 42 + 63 = 27)

就是一个简单的递归

用一个参数depth记录每次递归的深度。

代码

public class Solution {
    public int depthSum(List<NestedInteger> nestedList) {
        return helper(nestedList,1);
    }
    public int helper(List<NestedInteger> nestedList, int depth) {
        int sum = 0;
        for (NestedInteger ni : nestedList) {
            if (ni.isInteger()) {
                sum += ni.getInteger() * depth;
            } else {
                sum += helper(ni.getList(),depth+1);
            }
        }
        return sum;
    }
}

结果

nested-list-weight-sum-1