add 659

Author: fishercoder1534

README.md

@@ -22,6 +22,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|659|[Split Array into Consecutive Subsequences](https://leetcode.com/problems/split-array-into-consecutive-subsequences/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_659.java) | O(n) | O(n) | Medium | HashMap
 |657|[Judge Route Circle](https://leetcode.com/problems/judge-route-circle/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_657.java) | O(n) | O(1) | Easy | 
 |654|[Maximum Binary Tree](https://leetcode.com/problems/maximum-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_654.java) | O(n^2) | O(n) | Medium | Tree
 |653|[Two Sum IV - Input is a BST](https://leetcode.com/problems/two-sum-iv-input-is-a-bst/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_653.java) |  |  | Easy | Tree

src/main/java/com/fishercoder/solutions/_659.java

@@ -0,0 +1,61 @@
+package com.fishercoder.solutions;
+
+import java.util.*;
+
+/**
+ * 659. Split Array into Consecutive Subsequences
+ *
+ * You are given an integer array sorted in ascending order (may contain duplicates),
+ * you need to split them into several subsequences,
+ * where each subsequences consist of at least 3 consecutive integers. Return whether you can make such a split.
+
+ Example 1:
+ Input: [1,2,3,3,4,5]
+ Output: True
+ Explanation:
+ You can split them into two consecutive subsequences :
+ 1, 2, 3
+ 3, 4, 5
+
+ Example 2:
+ Input: [1,2,3,3,4,4,5,5]
+ Output: True
+ Explanation:
+ You can split them into two consecutive subsequences :
+ 1, 2, 3, 4, 5
+ 3, 4, 5
+
+ Example 3:
+ Input: [1,2,3,4,4,5]
+ Output: False
+
+ Note:
+ The length of the input is in range of [1, 10000]
+ */
+
+public class _659 {
+
+    /**reference: https://discuss.leetcode.com/topic/99187/java-o-n-time-o-n-space*/
+    public boolean isPossible(int[] nums) {
+        Map<Integer, Integer> freqMap = new HashMap<>();
+        for (int i : nums) {
+            freqMap.put(i, freqMap.getOrDefault(i, 0) + 1);
+        }
+        Map<Integer, Integer> appendFreqMap = new HashMap<>();
+        for (int i : nums) {
+            if (freqMap.get(i) == 0) {
+                continue;
+            } else if (appendFreqMap.getOrDefault(i, 0) > 0) {
+                appendFreqMap.put(i, appendFreqMap.get(i) - 1);
+                appendFreqMap.put(i+1, appendFreqMap.getOrDefault(i+1, 0) + 1);
+            } else if (freqMap.getOrDefault(i+1, 0) > 0 && freqMap.getOrDefault(i+2, 0) > 0) {
+                freqMap.put(i+1, freqMap.get(i+1) - 1);
+                freqMap.put(i+2, freqMap.get(i+2) - 1);
+                appendFreqMap.put(i+3, appendFreqMap.getOrDefault(i+3, 0) + 1);
+            } else return false;
+            freqMap.put(i, freqMap.get(i) - 1);
+        }
+        return true;
+    }
+
+}