Add all combination

src/main/java/com/thealgorithms/backtracking/AllCombination.java

@@ -0,0 +1,43 @@
+package com.thealgorithms.backtracking;
+
+import java.util.ArrayList;
+import java.util.List;
+public class AllCombination {
+    public static List<List<Integer>> combinations(int n, int k) {
+        List<List<Integer>> results = new ArrayList<>();
+        int[] nums = new int[n];
+
+        // Initialize the nums array with values from 1 to n
+        for (int i = 0; i < n; i++) {
+            nums[i] = i + 1;
+        }
+
+        backtrack(0, new ArrayList<Integer>(), nums, k, results);
+
+        return results;
+    }
+
+    private static void backtrack(int start, List<Integer> curr, int[] nums, int k, List<List<Integer>> results) {
+        if (curr.size() == k) {
+            results.add(new ArrayList<Integer>(curr));
+            return;
+        }
+
+        for (int i = start; i < nums.length; i++) {
+            curr.add(nums[i]);
+            backtrack(i + 1, curr, nums, k, results);
+            curr.remove(curr.size() - 1);
+        }
+    }
+
+    public static void main(String[] args) {
+        int n = 5;
+        int k = 3;
+        List<List<Integer>> results = combinations(n, k);
+
+        System.out.println("All possible combinations of " + k + " numbers out of 1 to " + n + ": ");
+        for (List<Integer> result : results) {
+            System.out.println(result.toString());
+        }
+    }
+}