Merge pull request Sunchit#1055 from MaheshReddy-05/master

August DLC in Java

Author: Sunchit

Leetcode2023/August2023/Java/Combinations.java

@@ -0,0 +1,26 @@
+// AUthor: Mahesh Reddy B N
+// Problem Link: https://leetcode.com/problems/combinations/description/
+
+class Solution {
+    public List<List<Integer>> combine(int n, int k) {
+        List<List<Integer>> ls = new ArrayList<>();
+        List<Integer> nums = new ArrayList<>();
+        for(int i=1;i<=n;i++){
+            nums.add(i);
+        }
+        List<Integer> al = new ArrayList<>();
+        helper(ls,al,nums,0,k);
+        return ls;
+    }
+    public void helper( List<List<Integer>> ls, List<Integer> al,List<Integer> nums,int si,int count){
+        if(count<=0){
+            ls.add(new ArrayList<>(al));
+            return;
+        }
+        if(si>=nums.size()) return;
+        al.add(nums.get(si));
+        helper(ls,al,nums,si+1,count-1);
+        al.remove(al.size()-1);
+        helper(ls,al,nums,si+1,count);
+    }
+}

Leetcode2023/August2023/Java/LetterCombinationsofaPhoneNumber.java

@@ -0,0 +1,35 @@
+// Author: Mahesh Reddy B N
+// Problem Link: https://leetcode.com/problems/letter-combinations-of-a-phone-number/description/
+
+
+class Solution {
+    public List<String> letterCombinations(String digits) {
+        String []str = new String[10];
+        str[2] = "abc";
+        str[3] = "def";
+        str[4] = "ghi";
+        str[5] = "jkl";
+        str[6] = "mno";
+        str[7] = "pqrs";
+        str[8] = "tuv";
+        str[9] = "wxyz";
+        List<String> al = new ArrayList<>();
+        helper(al,digits,str,0,"");
+        return al;
+    }
+    public void helper(List<String> al,String s,String[] str,int si,String cur){
+        if(si>= s.length()){
+            if(cur.length()>0){
+              al.add(cur);
+            }
+            return;
+        }
+        int curr = s.charAt(si) - '0';
+        for(int i=0;i<str[curr].length();i++){
+            String past = cur;
+            cur+= str[curr].charAt(i);
+            helper(al,s,str,si+1,cur);
+            cur = past;
+        }
+    }
+}

Leetcode2023/August2023/Java/Permutations.java

@@ -0,0 +1,25 @@
+// Author: Mahesh Reddy B N
+// Problem Link: https://leetcode.com/problems/permutations/
+
+class Solution {
+    public List<List<Integer>> permute(int[] nums) {
+        List<List<Integer>> ls = new ArrayList<>();
+        List<Integer> al = new ArrayList<>();
+        helper(ls,al,nums,0);
+        return ls;
+    }
+    public void helper(List<List<Integer>> ls, List<Integer> al,int[] nums,int count){
+        if(count>= nums.length){
+            ls.add(new ArrayList<>(al));
+            return;
+        }
+        for(int i=0;i<nums.length;i++){
+            if(nums[i]!=-11){
+                al.add(nums[i]);
+                nums[i] = -11;
+                helper(ls,al,nums,count+1);
+                nums[i] =  al.remove(al.size()-1);
+            }
+        }
+    }
+}