NestedListWeightSum339

Author: fluency03

Diff for: README.md

@@ -53,11 +53,11 @@
 | [Graph](https://github.com/fluency03/leetcode-java/blob/master/src/graph) |
 
 
-# Total: 510
+# Total: 511
 
 |   Easy  |  Medium | Hard |  -  |
 |:-------:|:-------:|:----:|:---:|
-|   137   |   279   |  83  | 11  |
+|   138   |   279   |  83  | 11  |
 
 
 | Question | Solution | Difficulty |
@@ -322,6 +322,7 @@
 | [336. Palindrome Pairs](https://leetcode.com/problems/palindrome-pairs/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/PalindromePairs336.java) | Hard |
 | [337. House Robber III](https://leetcode.com/problems/house-robber-iii/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/HouseRobberIII337.java) | Medium |
 | [338. Counting Bits](https://leetcode.com/problems/counting-bits/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/CountingBits338.java) | Medium |
+| [339. Nested List Weight Sum](https://leetcode.com/problems/nested-list-weight-sum/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/NestedListWeightSum339.java) | Easy |
 | [340. Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/LongestSubstringWithAtMostKDistinctCharacters340.java) | Hard |
 | [341. Flatten Nested List Iterator](https://leetcode.com/problems/flatten-nested-list-iterator/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/NestedIterator.java) | Medium |
 | [343. Integer Break](https://leetcode.com/problems/integer-break/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/IntegerBreak343.java) | Medium |

Diff for: src/NestedListWeightSum339.java

@@ -0,0 +1,66 @@
+/**
+ * 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;
+    }
+
+}