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)
递归地把乘积加上，每一层把level + 1得到正确的结果。
/**
* // 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) {
if (nestedList == null || nestedList.size() == 0) {
return 0;
}
int sum = dfs(nestedList, 1);
return sum;
}
private int dfs(List<NestedInteger> nestedList, int level) {
int curSum = 0;
for (NestedInteger ni : nestedList) {
if (ni.isInteger()) {
curSum += ni.getInteger() * level;
} else {
curSum += dfs(ni.getList(), level + 1);
}
}
return curSum;
}
}