414_Third_Maximum_Number

Author: qiyuangong

README.md

@@ -137,6 +137,7 @@ Also, there are open source implementations for basic data structs and algorithm
 | 408 | [Valid Word Abbreviation](https://leetcode.com/problems/valid-word-abbreviation/) ♥ | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/408_Valid_Word_Abbreviation.py) | Go over abbr and word, O(n) and O(1) |
 | 409 | [Longest Palindrome](https://leetcode.com/problems/longest-palindrome/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/409_Longest_Palindrome.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/409_Longest_Palindrome.java) | Length of Palindrome is always 2n or 2n + 1. So, get all possible 2*n, and choose a single one as 1 if it exists. |
 | 412 | [Fizz Buzz](https://leetcode.com/problems/fizz-buzz/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/412_Fizz_Buzz.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/412_Fizz_Buzz.java) | 1. From 1 to n, condition check<br>2. Condition check and string connect |
+| 414 | [Third Maximum Number](https://leetcode.com/problems/third-maximum-number/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/414_Third_Maximum_Number.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/414_Third_Maximum_Number.java) | 1. Keep max 1-3 then compare, O(n) and O(1)<br>2. PriorityQueue, O(n) and O(1) |
 | 415 | [Add Strings](https://leetcode.com/problems/add-strings/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/415_Add_Strings.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/415_Add_Strings.java) | Two points, careful abour carry, O(n) and O(n) |
 | 416 | [Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/416_Partition_Equal_Subset_Sum.py) | DP, Check if sum of some elements can be half of total sum, O(total_sum / 2 * n) and O(total_sum / 2) |
 | 421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/421_Maximum_XOR_of_Two_Numbers_in_an_Array.py) | Check 0~32 prefix, check if there is x y in prefixes, where x ^ y = answer ^ 1, O(32n) and O(n) |

java/414_Third_Maximum_Number.java

@@ -0,0 +1,16 @@
+public class Solution {
+    public int thirdMax(int[] nums) {
+        PriorityQueue<Integer> pq = new PriorityQueue<>(3);
+        Set<Integer> set = new HashSet<>();
+        for (int i : nums) {
+            if (set.contains(i)) continue;
+            pq.offer(i);
+            set.add(i);
+            if (pq.size() > 3) set.remove(pq.poll());
+        }
+        while (pq.size() < 3 && pq.size() > 1) {
+            pq.poll();
+        }
+        return pq.peek();
+    }
+}

python/414_Third_Maximum_Number.py

@@ -0,0 +1,20 @@
+class Solution(object):
+    def thirdMax(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        import Queue
+        pq = Queue.PriorityQueue(4)
+        check = set()
+        for n in nums:
+            if n in check:
+                continue
+            pq.put(n)
+            check.add(n)
+            if len(check) > 3:
+                check.remove(pq.get())
+        total = len(check)
+        while total < 3 and total > 1:
+            total -= 1
+        return pq.get()