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/**

* 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:

* Input: [[1,1],2,[1,1]]

* Output: 10

* Explanation: Four 1's at depth 2, one 2 at depth 1.

*

* Example 2:

* Input: [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.

*/

/**

* // 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 NestedListWeightSum339 {

public int depthSum(List<NestedInteger> nestedList) {

return depthSum(nestedList, 1);

}

private int depthSum(List<NestedInteger> nestedList, int level) {

int res = 0;

for (NestedInteger ni: nestedList) {

if (ni.isInteger()) {

res += ni.getInteger() * level;

} else {

res += depthSum(ni.getList(), level + 1);

}

}

return res;

}

}