added modified solution for LongestConsecutiveSequence.java

Author: Kevin Naughton Jr

company/facebook/LongestConsecutiveSequence.java

@@ -6,27 +6,32 @@
 
 // Your algorithm should run in O(n) complexity.
 
-public class LongestConsecutiveSequence {
+class LongestConsecutiveSequence {
     public int longestConsecutive(int[] nums) {
-        int res = 0;
-        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
+        if(nums == null || nums.length == 0) {
+            return 0;
+        }
+        
+        Set<Integer> set = new HashSet<Integer>();
+        for(int n: nums) {
+            set.add(n);
+        }
 
-        for(int n : nums) {
-            if(!map.containsKey(n)) {
-                int left = (map.containsKey(n - 1)) ? map.get(n - 1) : 0;
-                int right = (map.containsKey(n + 1)) ? map.get(n + 1) : 0;
+        int maxLength = 0;
+        for(int n: set) {
+            if(!set.contains(n - 1)) {
+                int current = n;
+                int currentMax = 1;
 
-                int sum = left + right + 1;
-                map.put(n, sum);
-                res = Math.max(res, sum);
+                while(set.contains(n + 1)) {
+                    currentMax++;
+                    n++;
+                }
 
-                map.put(n - left, sum);
-                map.put(n + right, sum);
-            } else {
-                continue;
+                maxLength = Math.max(maxLength, currentMax);
             }
         }
 
-        return res;
+        return maxLength;
     }
 }

company/google/LongestConsecutiveSequence.java

@@ -6,27 +6,32 @@
 
 // Your algorithm should run in O(n) complexity.
 
-public class LongestConsecutiveSequence {
+class LongestConsecutiveSequence {
     public int longestConsecutive(int[] nums) {
-        int res = 0;
-        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
+        if(nums == null || nums.length == 0) {
+            return 0;
+        }
+        
+        Set<Integer> set = new HashSet<Integer>();
+        for(int n: nums) {
+            set.add(n);
+        }
 
-        for(int n : nums) {
-            if(!map.containsKey(n)) {
-                int left = (map.containsKey(n - 1)) ? map.get(n - 1) : 0;
-                int right = (map.containsKey(n + 1)) ? map.get(n + 1) : 0;
+        int maxLength = 0;
+        for(int n: set) {
+            if(!set.contains(n - 1)) {
+                int current = n;
+                int currentMax = 1;
 
-                int sum = left + right + 1;
-                map.put(n, sum);
-                res = Math.max(res, sum);
+                while(set.contains(n + 1)) {
+                    currentMax++;
+                    n++;
+                }
 
-                map.put(n - left, sum);
-                map.put(n + right, sum);
-            } else {
-                continue;
+                maxLength = Math.max(maxLength, currentMax);
             }
         }
 
-        return res;
+        return maxLength;
     }
 }

leetcode/array/LongestConsecutiveSequence.java

@@ -6,27 +6,32 @@
 
 // Your algorithm should run in O(n) complexity.
 
-public class LongestConsecutiveSequence {
+class LongestConsecutiveSequence {
     public int longestConsecutive(int[] nums) {
-        int res = 0;
-        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
+        if(nums == null || nums.length == 0) {
+            return 0;
+        }
+        
+        Set<Integer> set = new HashSet<Integer>();
+        for(int n: nums) {
+            set.add(n);
+        }
 
-        for(int n : nums) {
-            if(!map.containsKey(n)) {
-                int left = (map.containsKey(n - 1)) ? map.get(n - 1) : 0;
-                int right = (map.containsKey(n + 1)) ? map.get(n + 1) : 0;
+        int maxLength = 0;
+        for(int n: set) {
+            if(!set.contains(n - 1)) {
+                int current = n;
+                int currentMax = 1;
 
-                int sum = left + right + 1;
-                map.put(n, sum);
-                res = Math.max(res, sum);
+                while(set.contains(n + 1)) {
+                    currentMax++;
+                    n++;
+                }
 
-                map.put(n - left, sum);
-                map.put(n + right, sum);
-            } else {
-                continue;
+                maxLength = Math.max(maxLength, currentMax);
             }
         }
 
-        return res;
+        return maxLength;
     }
 }