Question

339. Nested List Weight Sum

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Description

You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists.

The depth of an integer is the number of lists that it is inside of. For example, the nested list [1,[2,2],[[3],2],1] has each integer's value set to its depth.

Return _the sum of each integer in _nestedList_ multiplied by its depth_.

 

Example 1:

Input: nestedList = [[1,1],2,[1,1]]
Output: 10
Explanation: Four 1's at depth 2, one 2 at depth 1. 1*2 + 1*2 + 2*1 + 1*2 + 1*2 = 10.

Example 2:

Input: nestedList = [1,[4,[6]]]
Output: 27
Explanation: One 1 at depth 1, one 4 at depth 2, and one 6 at depth 3. 1*1 + 4*2 + 6*3 = 27.

Example 3:

Input: nestedList = [0]
Output: 0

 

Constraints:

• 1 <= nestedList.length <= 50
• The values of the integers in the nested list is in the range [-100, 100].
• The maximum depth of any integer is less than or equal to 50.

Solutions

Solution 1

# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
# class NestedInteger:
#  def __init__(self, value=None):
#    """
#    If value is not specified, initializes an empty list.
#    Otherwise initializes a single integer equal to value.
#    """
#
#  def isInteger(self):
#    """
#    @return True if this NestedInteger holds a single integer, rather than a nested list.
#    :rtype bool
#    """
#
#  def add(self, elem):
#    """
#    Set this NestedInteger to hold a nested list and adds a nested integer elem to it.
#    :rtype void
#    """
#
#  def setInteger(self, value):
#    """
#    Set this NestedInteger to hold a single integer equal to value.
#    :rtype void
#    """
#
#  def getInteger(self):
#    """
#    @return the single integer that this NestedInteger holds, if it holds a single integer
#    Return None if this NestedInteger holds a nested list
#    :rtype int
#    """
#
#  def getList(self):
#    """
#    @return the nested list that this NestedInteger holds, if it holds a nested list
#    Return None if this NestedInteger holds a single integer
#    :rtype List[NestedInteger]
#    """
class Solution:
  def depthSum(self, nestedList: List[NestedInteger]) -> int:
    def dfs(nestedList, depth):
      depth_sum = 0
      for item in nestedList:
        if item.isInteger():
          depth_sum += item.getInteger() * depth
        else:
          depth_sum += dfs(item.getList(), depth + 1)
      return depth_sum

    return dfs(nestedList, 1)

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * public interface NestedInteger {
 *   // Constructor initializes an empty nested list.
 *   public NestedInteger();
 *
 *   // Constructor initializes a single integer.
 *   public NestedInteger(int value);
 *
 *   // @return true if this NestedInteger holds a single integer, rather than a nested list.
 *   public boolean isInteger();
 *
 *   // @return the single integer that this NestedInteger holds, if it holds a single integer
 *   // Return null if this NestedInteger holds a nested list
 *   public Integer getInteger();
 *
 *   // Set this NestedInteger to hold a single integer.
 *   public void setInteger(int value);
 *
 *   // Set this NestedInteger to hold a nested list and adds a nested integer to it.
 *   public void add(NestedInteger ni);
 *
 *   // @return the nested list that this NestedInteger holds, if it holds a nested list
 *   // Return empty list if this NestedInteger holds a single integer
 *   public List<NestedInteger> getList();
 * }
 */
class Solution {
  public int depthSum(List<NestedInteger> nestedList) {
    return dfs(nestedList, 1);
  }

  private int dfs(List<NestedInteger> nestedList, int depth) {
    int depthSum = 0;
    for (NestedInteger item : nestedList) {
      if (item.isInteger()) {
        depthSum += item.getInteger() * depth;
      } else {
        depthSum += dfs(item.getList(), depth + 1);
      }
    }
    return depthSum;
  }
}

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * function NestedInteger() {
 *
 *   Return true if this NestedInteger holds a single integer, rather than a nested list.
 *   @return {boolean}
 *   this.isInteger = function() {
 *     ...
 *   };
 *
 *   Return the single integer that this NestedInteger holds, if it holds a single integer
 *   Return null if this NestedInteger holds a nested list
 *   @return {integer}
 *   this.getInteger = function() {
 *     ...
 *   };
 *
 *   Set this NestedInteger to hold a single integer equal to value.
 *   @return {void}
 *   this.setInteger = function(value) {
 *     ...
 *   };
 *
 *   Set this NestedInteger to hold a nested list and adds a nested integer elem to it.
 *   @return {void}
 *   this.add = function(elem) {
 *     ...
 *   };
 *
 *   Return the nested list that this NestedInteger holds, if it holds a nested list
 *   Return null if this NestedInteger holds a single integer
 *   @return {NestedInteger[]}
 *   this.getList = function() {
 *     ...
 *   };
 * };
 */
/**
 * @param {NestedInteger[]} nestedList
 * @return {number}
 */
var depthSum = function (nestedList) {
  const dfs = (nestedList, depth) => {
    let depthSum = 0;
    for (const item of nestedList) {
      if (item.isInteger()) {
        depthSum += item.getInteger() * depth;
      } else {
        depthSum += dfs(item.getList(), depth + 1);
      }
    }
    return depthSum;
  };
  return dfs(nestedList, 1);
};