Leetcode 339. Nested List Weight Sum & 364. Nested List Weight Sum II

339. Nested List Weight Sum

Total Accepted: 9434 Total Submissions: 16027 Difficulty: Easy

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 + 4*2 + 6*3 = 27)

Hide Company Tags
 LinkedIn

Hide Tags
 Depth-first Search

Hide Similar Problems
 (M) Nested List Weight Sum II

思路：

递归。每次碰到list depth++。

/**
* // This is the interface that allows for creating nested lists.
* // You should not implement it, or speculate about its implementation
* public interface NestedInteger {
*
* // @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();
*
* // @return the nested list that this NestedInteger holds, if it holds a nested list
* // Return null if this NestedInteger holds a single integer
* public List<NestedInteger> getList();
* }
*/
public class Solution {
public int depthSum(List<NestedInteger> nestedList) {
int res = helper(nestedList, 1);
return res;
}

public int helper(List<NestedInteger> list, int weight){
int sum = 0;
for(NestedInteger item : list){
if(item.isInteger()) sum += item.getInteger() * weight;
else sum += helper(item.getList(), weight + 1);
}
return sum;
}
}

364. Nested List Weight Sum II

Total Accepted: 5021 Total Submissions: 10233 Difficulty: Medium

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.
Different from the previous question where weight
is increasing from root to leaf, now the weight is defined from bottom up. i.e., the leaf level integers 
have weight 1, and the root level integers have the largest weight.
Example 1:

Given the list 

[[1,1],2,[1,1]]

, return 8. (four 1's
at depth 1, one 2 at depth 2)
Example 2:

Given the list 

[1,[4,[6]]]

, return 17. (one 1 at
depth 3, one 4 at depth 2, and one 6 at depth 1; 1*3 + 4*2 + 6*1 = 17)

Hide Company Tags
 LinkedIn

Hide Tags
 Depth-first Search

Hide Similar Problems
 (E) Nested List Weight Sum

思路：

先求一遍最大深度。然后call一遍I的代码，区别是碰到list depth--。

/**
* // 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 null if this NestedInteger holds a single integer
*     public List<NestedInteger> getList();
* }
*/
public class Solution {
int maxDepth = 0;
public int depthSumInverse(List<NestedInteger> nestedList) {
dfs(nestedList, 1);
return  helper(nestedList, maxDepth);
}

public int helper(List<NestedInteger> list, int weight){
int sum = 0;
for(NestedInteger item : list){
if(item.isInteger()) sum += item.getInteger() * weight;
else sum += helper(item.getList(), weight - 1);
}
return sum;
}

public void dfs(List<NestedInteger> list, int d){
if(d > maxDepth) maxDepth = d;

for(NestedInteger item : list){
if(item.isInteger()) continue;
else dfs(item.getList(), d + 1);
}
}
}