LintCode 551: Nested List Weight Sum

最新推荐文章于 2025-08-12 11:46:39 发布

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本文介绍了一种名为深度加权求和的算法，该算法用于处理嵌套的整数列表，通过递归的方式计算所有整数的加权总和，其中权重由元素的深度决定。文章提供了具体的代码实现，包括如何遍历嵌套列表并根据深度计算每个元素的权重。

Nested List Weight Sum
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
Given the list [[1,1],2,[1,1]], return 10. (four 1’s at depth 2, one 2 at depth 1, 4 * 1 * 2 + 1 * 2 * 1 = 10)
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 + 4 * 2 + 6 * 3 = 27)

思路：递归。
代码如下：

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Return true if this NestedInteger holds a single integer,
 *     // rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds,
 *     // if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Return the nested list that this NestedInteger holds,
 *     // if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */
class Solution {
public:
    int depthSum(const vector<NestedInteger>& nestedList) {
        int result = 0;
        
        for (auto i : nestedList) {
            result += helper(i, 1);
        }
        
        return result;
    }
    
    int helper(const NestedInteger &nestInt, int depth) {
        if (nestInt.isInteger()) return nestInt.getInteger() * depth;
        
        int len = nestInt.getList().size();
        int result = 0;
        vector<NestedInteger> nestList = nestInt.getList();
        for (int i = 0; i < len; ++i) {
            result += helper(nestList[i], (depth + 1));
        }
        return result;
    }
};