* // 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 int depthSum(List<NestedInteger> nestedList) {
if (nestedList == null || nestedList.size() == 0) {
return getDepthSum(nestedList, 1);
public int getDepthSum(List<NestedInteger> nestedList, int depth) {
for (NestedInteger ni : nestedList) {
res += ni.isInteger() ? ni.getInteger() * depth : getDepthSum(ni.getList(), depth + 1);