1118

Author: surajr

README.md

@@ -41,6 +41,8 @@ Feel free to submit pull requests, add issues and be a contributer.
 |---------------- |---------------- | ----------- | --------------- | --------------- | ------------- |-----|
 | Leetcode | [12. Integer to Roman](https://leetcode.com/problems/integer-to-roman/description/) | [Java](./java/intToRoman.java)  | _O(n)_       | _O(1)_          |  Medium      |         |
 | Leetcode | [31. Next Permutation](https://leetcode.com/problems/next-permutation/description/) | [Java](./java/nextPermutation.java)  | _O(n)_       | _O(1)_          |  Easy       |         |
+| Leetcode | [39. Combination Sum](https://leetcode.com/problems/combination-sum/description/) | [Java](./java/combinationSum.java)  | _O(2^n)_       | _O(1)_          |  Medium       |         |
+| Leetcode | [40. Combination Sum II](https://leetcode.com/problems/combination-sum-ii/description/) | [Java](./java/combinationSumii.java)  | _O(2^n)_       | _O(1)_          |  Medium       |         |
 | Leetcode | [46. Permutations](https://leetcode.com/problems/permutations/description/) | [Java](./java/permute.java)  | _O(2^n)_       | _O(1)_          |  Medium       |         |
 | Leetcode | [47. Permutations II](https://leetcode.com/problems/permutations-ii/description/) | [Java](./java/permuteUnique.java)  | _O(2^n)_       | _O(1)_          |  Medium       |         |
 | Leetcode | [66. Plus One](https://leetcode.com/problems/plus-one/description/) | [Java](./java/plusOne.java)  | _O(n)_       | _O(1)_          |  Easy       |         |
@@ -75,6 +77,7 @@ Feel free to submit pull requests, add issues and be a contributer.
 |---------------- |---------------- | ----------- | --------------- | --------------- | ------------- |-----|
 | Leetcode  | [6. ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/description/) | [Java](./java/ZigZag.java)  | _O(n)_       | _O(n)_          |  Medium      |         |
 | Leetcode  | [125. Valid Palindrome](https://leetcode.com/problems/valid-palindrome/description/) | [Java](./java/isPalindrome.java)  | _O(n)_       | _O(1)_          |  Easy       |         |
+| Leetcode  | [131. Palindrome Partitioning](https://leetcode.com/problems/palindrome-partitioning/description/) | [Java](./java/PalindromePartition.java)  | _O(2^n)_       | _O(1)_          |  Medium       |         |
 | Leetcode  | [139. Word Break](https://leetcode.com/problems/word-break/description/) | [Java](./java/wordBreak.java)  | _O(n^2)_       | _O(n)_          |  Medium       |         |
 | Leetcode  | [151. Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/description/) | [Java](./java/reverseWords1.java)  | _O(n)_       | _O(1)_          |  Easy       |         |
 | Leetcode  | [165. Compare Version Numbers](https://leetcode.com/problems/compare-version-numbers/description/) | [Java](./java/compareVersion.java)  | _O(n)_       | _O(1)_          |  Medium       |         |

java/PalindromePartition.java

@@ -0,0 +1,34 @@
+class Solution {
+    public List<List<String>> partition(String s) {
+        List<List<String>> result = new ArrayList<>();
+        backtrack(result, s, new ArrayList<String>(), 0);
+        return result;
+    }
+    
+    public void backtrack(List<List<String>> result, String s, List<String> temp, int start)
+    {
+        if(start == s.length())
+            result.add(new ArrayList<String>(temp));
+        else
+        {
+            for(int i=start; i<s.length(); i++)
+            {
+                if(isPalindrome(s, start, i))
+                {
+                    temp.add(s.substring(start, i+1));
+                    backtrack(result, s, temp, i+1);
+                    temp.remove(temp.size()-1);
+                }
+            }
+        }
+    }
+    
+    public boolean isPalindrome(String s, int left, int right)
+    {
+        while(left < right)
+        {
+            if(s.charAt(left++) != s.charAt(right--)) return false;
+        }
+        return true;
+    }
+}

java/combinationSum.java

@@ -0,0 +1,23 @@
+class Solution {
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        List<List<Integer>> result = new ArrayList<>();
+        Arrays.sort(candidates);
+        backtrack(candidates, result, new ArrayList<Integer>(), target, 0);
+        return result;
+    }
+    
+    public void backtrack(int [] candidates, List<List<Integer>> result, List<Integer> temp, int stepDiff, int start)
+    {
+        if(stepDiff < 0) return;
+        else if(stepDiff == 0) result.add(new ArrayList<Integer>(temp));
+        else
+        {
+            for(int i=start; i<candidates.length; i++)
+            {
+                temp.add(candidates[i]);
+                backtrack(candidates, result, temp, stepDiff-candidates[i], i);
+                temp.remove(temp.size()-1);
+            }
+        }
+    }
+}

java/combinationSumii.java

@@ -0,0 +1,24 @@
+class Solution {
+    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
+        List<List<Integer>> result = new ArrayList<>();
+        Arrays.sort(candidates);
+        backtrack(candidates, result, new ArrayList<Integer>(), target, 0);
+        return result;
+    }
+    
+    public void backtrack(int [] candidates, List<List<Integer>> result, List<Integer> temp, int stepDiff, int start)
+    {
+        if(stepDiff < 0) return;
+        else if(stepDiff == 0) result.add(new ArrayList<Integer>(temp));
+        else
+        {
+            for(int i=start; i<candidates.length; i++)
+            {
+                if(i>start && candidates[i] == candidates[i-1]) continue;
+                temp.add(candidates[i]);
+                backtrack(candidates, result, temp, stepDiff-candidates[i], i+1);
+                temp.remove(temp.size()-1);
+            }
+        }
+    }
+}