From 8c3d8d60e1d008f8f6ac3c00a3dc5e9a0d72c802 Mon Sep 17 00:00:00 2001
From: Christian R <108245334+evaunit00@users.noreply.github.com>
Date: Wed, 6 Jul 2022 14:46:11 -0700
Subject: [PATCH 1/4] Add files via upload

Created and finished 39. Combination Sum and 17. Letter Combinations of a Phone Number
---
 17-Letter-Combinations-of-a-Phone-Number.java | 37 +++++++++++++++++++
 39-Combination-Sum.java                       | 24 ++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 17-Letter-Combinations-of-a-Phone-Number.java
 create mode 100644 39-Combination-Sum.java

diff --git a/17-Letter-Combinations-of-a-Phone-Number.java b/17-Letter-Combinations-of-a-Phone-Number.java
new file mode 100644
index 000000000..def598a17
--- /dev/null
+++ b/17-Letter-Combinations-of-a-Phone-Number.java
@@ -0,0 +1,37 @@
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+class Solution {
+    private Map<Character, String> digitToChar = Map.of(
+        '2', "abc", '3', "def", '4', "ghi", '5', "jkl",
+        '6', "mno", '7', "pqrs", '8', "tuv", '9', "wxyz");
+    
+    public List<String> letterCombinations(String digits) {
+     
+        if (digits.length() == 0) {
+            return new ArrayList();
+        }
+        
+        List<String> ans = new ArrayList();
+        String cur = "";
+        backtrack(digits, ans, cur, 0);
+        return ans;
+        
+    }
+    
+    public void backtrack(String digits, List<String> ans, String cur, int index) {
+        
+        if (cur.length() == digits.length()) {
+            ans.add(cur);
+            return;
+        } else if (index >= digits.length()) {
+            return;
+        } else {
+            String digit = digitToChar.get(digits.charAt(index));
+            for (char c : digit.toCharArray()) {
+                backtrack(digits, ans, cur + c, index + 1);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/39-Combination-Sum.java b/39-Combination-Sum.java
new file mode 100644
index 000000000..e3b0f4730
--- /dev/null
+++ b/39-Combination-Sum.java
@@ -0,0 +1,24 @@
+class Solution {
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        List<List<Integer>> ans = new ArrayList<List<Integer>>();
+        List<Integer> cur = new ArrayList();
+        backtrack(candidates, target, ans, cur, 0);
+        return ans;
+        
+    }
+    
+    public void backtrack(int[] candidates, int target, List<List<Integer>> ans, List<Integer> cur, int index) {
+        if (target == 0) {
+            ans.add(new ArrayList(cur));
+        } else if (target < 0 || index >= candidates.length) {
+            return;
+        } else {
+            cur.add(candidates[index]);
+            backtrack(candidates, target - candidates[index], ans, cur, index);
+            
+            cur.remove(cur.get(cur.size() - 1));
+            backtrack(candidates, target, ans, cur, index + 1);
+        }
+        
+    }    
+}
\ No newline at end of file

From 886d7d4d7947240e0fc1d30825823189356b50d0 Mon Sep 17 00:00:00 2001
From: Christian R <108245334+evaunit00@users.noreply.github.com>
Date: Wed, 6 Jul 2022 14:48:16 -0700
Subject: [PATCH 2/4] Delete 17-Letter-Combinations-of-a-Phone-Number.java

Accidentally added it to python directory instead of java
---
 17-Letter-Combinations-of-a-Phone-Number.java | 37 -------------------
 1 file changed, 37 deletions(-)
 delete mode 100644 17-Letter-Combinations-of-a-Phone-Number.java

diff --git a/17-Letter-Combinations-of-a-Phone-Number.java b/17-Letter-Combinations-of-a-Phone-Number.java
deleted file mode 100644
index def598a17..000000000
--- a/17-Letter-Combinations-of-a-Phone-Number.java
+++ /dev/null
@@ -1,37 +0,0 @@
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Map;
-
-class Solution {
-    private Map<Character, String> digitToChar = Map.of(
-        '2', "abc", '3', "def", '4', "ghi", '5', "jkl",
-        '6', "mno", '7', "pqrs", '8', "tuv", '9', "wxyz");
-    
-    public List<String> letterCombinations(String digits) {
-     
-        if (digits.length() == 0) {
-            return new ArrayList();
-        }
-        
-        List<String> ans = new ArrayList();
-        String cur = "";
-        backtrack(digits, ans, cur, 0);
-        return ans;
-        
-    }
-    
-    public void backtrack(String digits, List<String> ans, String cur, int index) {
-        
-        if (cur.length() == digits.length()) {
-            ans.add(cur);
-            return;
-        } else if (index >= digits.length()) {
-            return;
-        } else {
-            String digit = digitToChar.get(digits.charAt(index));
-            for (char c : digit.toCharArray()) {
-                backtrack(digits, ans, cur + c, index + 1);
-            }
-        }
-    }
-}
\ No newline at end of file

From 137ca09a5ca9084a346b1ff8190fd3826327cf35 Mon Sep 17 00:00:00 2001
From: Christian R <108245334+evaunit00@users.noreply.github.com>
Date: Wed, 6 Jul 2022 14:49:08 -0700
Subject: [PATCH 3/4] Delete 39-Combination-Sum.java

Accidentally added to python directory instead of Java
---
 39-Combination-Sum.java | 24 ------------------------
 1 file changed, 24 deletions(-)
 delete mode 100644 39-Combination-Sum.java

diff --git a/39-Combination-Sum.java b/39-Combination-Sum.java
deleted file mode 100644
index e3b0f4730..000000000
--- a/39-Combination-Sum.java
+++ /dev/null
@@ -1,24 +0,0 @@
-class Solution {
-    public List<List<Integer>> combinationSum(int[] candidates, int target) {
-        List<List<Integer>> ans = new ArrayList<List<Integer>>();
-        List<Integer> cur = new ArrayList();
-        backtrack(candidates, target, ans, cur, 0);
-        return ans;
-        
-    }
-    
-    public void backtrack(int[] candidates, int target, List<List<Integer>> ans, List<Integer> cur, int index) {
-        if (target == 0) {
-            ans.add(new ArrayList(cur));
-        } else if (target < 0 || index >= candidates.length) {
-            return;
-        } else {
-            cur.add(candidates[index]);
-            backtrack(candidates, target - candidates[index], ans, cur, index);
-            
-            cur.remove(cur.get(cur.size() - 1));
-            backtrack(candidates, target, ans, cur, index + 1);
-        }
-        
-    }    
-}
\ No newline at end of file

From 9d8b53abcb0f6f5093db4060d745a666c6087a53 Mon Sep 17 00:00:00 2001
From: Christian R <108245334+evaunit00@users.noreply.github.com>
Date: Wed, 6 Jul 2022 14:51:30 -0700
Subject: [PATCH 4/4] Added questions 17 and 39 in Java

Added question 17. Letter Combinations of a Phone Number and 39. Combination Sum in Java
---
 ...Letter-Combinations-of-a-Phone-Number.java | 37 +++++++++++++++++++
 java/39-Combination-Sum.java                  | 24 ++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 java/17-Letter-Combinations-of-a-Phone-Number.java
 create mode 100644 java/39-Combination-Sum.java

diff --git a/java/17-Letter-Combinations-of-a-Phone-Number.java b/java/17-Letter-Combinations-of-a-Phone-Number.java
new file mode 100644
index 000000000..def598a17
--- /dev/null
+++ b/java/17-Letter-Combinations-of-a-Phone-Number.java
@@ -0,0 +1,37 @@
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+class Solution {
+    private Map<Character, String> digitToChar = Map.of(
+        '2', "abc", '3', "def", '4', "ghi", '5', "jkl",
+        '6', "mno", '7', "pqrs", '8', "tuv", '9', "wxyz");
+    
+    public List<String> letterCombinations(String digits) {
+     
+        if (digits.length() == 0) {
+            return new ArrayList();
+        }
+        
+        List<String> ans = new ArrayList();
+        String cur = "";
+        backtrack(digits, ans, cur, 0);
+        return ans;
+        
+    }
+    
+    public void backtrack(String digits, List<String> ans, String cur, int index) {
+        
+        if (cur.length() == digits.length()) {
+            ans.add(cur);
+            return;
+        } else if (index >= digits.length()) {
+            return;
+        } else {
+            String digit = digitToChar.get(digits.charAt(index));
+            for (char c : digit.toCharArray()) {
+                backtrack(digits, ans, cur + c, index + 1);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/java/39-Combination-Sum.java b/java/39-Combination-Sum.java
new file mode 100644
index 000000000..e3b0f4730
--- /dev/null
+++ b/java/39-Combination-Sum.java
@@ -0,0 +1,24 @@
+class Solution {
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        List<List<Integer>> ans = new ArrayList<List<Integer>>();
+        List<Integer> cur = new ArrayList();
+        backtrack(candidates, target, ans, cur, 0);
+        return ans;
+        
+    }
+    
+    public void backtrack(int[] candidates, int target, List<List<Integer>> ans, List<Integer> cur, int index) {
+        if (target == 0) {
+            ans.add(new ArrayList(cur));
+        } else if (target < 0 || index >= candidates.length) {
+            return;
+        } else {
+            cur.add(candidates[index]);
+            backtrack(candidates, target - candidates[index], ans, cur, index);
+            
+            cur.remove(cur.get(cur.size() - 1));
+            backtrack(candidates, target, ans, cur, index + 1);
+        }
+        
+    }    
+}
\ No newline at end of file

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