Description
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
Example 1:
Input: the list [[1,1],2,[1,1]], Output: 10. Explanation: four 1's at depth 2, one 2 at depth 1, 4 * 1 * 2 + 1 * 2 * 1 = 10
Example 2:
Input: the list [1,[4,[6]]],
Output: 27.
Explanation:
one 1 at depth 1, one 4 at depth 2, and one 6 at depth 3; 1 + 4 * 2 + 6 * 3 = 27
思路：dfs 按照深度带权求和/**
* // 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) {
return helper(nestedList, 1);
}
public int helper(List<NestedInteger> nestedList, int depth){
if (nestedList == null || nestedList.size() == 0)
return 0;
int sum = 0;
for(NestedInteger ele : nestedList) {
if (ele.isInteger()) {
sum += ele.getInteger() * depth;
} else {
sum += helper(ele.getList(), depth + 1);
}
}
return sum;
}
}