diff --git a/src/Practice.java b/src/Practice.java
index 6795da7..a0fb8a0 100644
--- a/src/Practice.java
+++ b/src/Practice.java
@@ -5,8 +5,9 @@
 
 public class Practice {
 
-  // Time Complexity:
-  // Space Complexity: 
+  // Time Complexity: 0(n)
+  // Space Complexity: 0(n)
+  
   public static List<Integer> findEvens(int[] array) {
     List<Integer> evens = new ArrayList<>();
     for (int num : array) {
@@ -17,8 +18,8 @@ public static List<Integer> findEvens(int[] array) {
     return evens;
   }
 
-  // Time Complexity:
-  // Space Complexity: 
+  // Time Complexity: 0(n)
+  // Space Complexity: 0(1)
   public static int sumDiagonal(int[][] matrix) {
     int sum = 0;
     for (int i = 0; i < matrix.length; i++) {
@@ -28,8 +29,8 @@ public static int sumDiagonal(int[][] matrix) {
   }
   
 
-  // Time Complexity: 
-  // Space Complexity: 
+  // Time Complexity: 0(n)
+  // Space Complexity: 0(n)
   // Does the 'T' look confusing? Consider refreshing on generic methods
   // We'll revisit generics as a class later
   public static <T> Map<T, Integer> countFrequencies(T[] array) {
@@ -40,8 +41,8 @@ public static <T> Map<T, Integer> countFrequencies(T[] array) {
     return frequencies;
   }
 
-  // Time Complexity: 
-  // Space Complexity: 
+  // Time Complexity: 0(n2)
+  // Space Complexity: 0(n)
   public static List<Integer> evensToSquare(int n) {
     List<Integer> evens = new ArrayList<>();
     for(int i = 0; i <= n*n; i+=2) {
@@ -68,8 +69,25 @@ public static List<Integer> evensToSquare(int n) {
   public static int mostCommonTimeEfficient(int[] nums) {
     // TODO: Complete this method with an implementation that runs
     // in O(n) time. n = nums.size()
-    return -1;
+    if (nums == null || nums.length == 0) {
+      throw new IllegalArgumentException("Invalid input");
+  }
+  
+  Map<Integer, Integer> counts = new HashMap<>();
+  int result = nums[0];
+  int max = 1;
+  
+  for (int num : nums) {
+      int count = counts.getOrDefault(num, 0) + 1;
+      counts.put(num, count);
+      if (count > max) {
+          max = count;
+          result = num;
+      }
   }
+  
+  return result;
+}
 
   /**
    * Returns the integer that shows up most frequently in an array.
@@ -80,15 +98,36 @@ public static int mostCommonTimeEfficient(int[] nums) {
    * 
    * Once you finish, WRITE TESTS FOR IT in PracticeTest.java
    * 
-   * Time Complexity: 
-   * Space Complexity: 
+   * Time Complexity: 0(n2)
+   * Space Complexity: 0(1)
    * 
    * @param nums An array of integers
    * @return the integer that shows up most commonly
    */
-  public static int mostCommonSpaceEfficient(int[] nums) {
-    // TODO: Complete this method with an implementation that runs
-    // in O(1) space.
-    return -1;
-  }
+ public static int mostCommonSpaceEfficient(int[] nums) {
+    if (nums == null || nums.length == 0) {
+        throw new IllegalArgumentException("Input array is empty or null");
+    }
+    
+    int maxCount = 0;
+    int mostCommon = nums[0];
+    
+    for (int i = 0; i < nums.length; i++) {
+        int currentNum = nums[i];
+        int currentCount = 0;
+        
+        for (int j = 0; j < nums.length; j++) {
+            if (nums[j] == currentNum) {
+                currentCount++;
+            }
+        }
+        
+        if (currentCount > maxCount) {
+            maxCount = currentCount;
+            mostCommon = currentNum;
+        }
+    }
+    
+    return mostCommon;
+}
 }
\ No newline at end of file
diff --git a/src/PracticeTest.java b/src/PracticeTest.java
index 4242545..8bc3078 100644
--- a/src/PracticeTest.java
+++ b/src/PracticeTest.java
@@ -1,10 +1,43 @@
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.util.HashMap;
+import java.util.Map;
+
 
 public class PracticeTest {
   
   // TODO: Implement tests for Practice.mostCommonTimeEfficient and Practice.mostCommonSpaceEfficient
+    // Tests for mostCommonTimeEfficient
+    public static void main(String[] args) {
+      testMostCommon();
+  }
+  
+  public static void testMostCommon() {
+      
+      int result1 = Practice.mostCommonTimeEfficient(new int[]{1,2,3,3});
+      System.out.println("Test 1: " + (result1 == 3 ? "PASSED" : "FAILED"));
+      
+      
+      int result2 = Practice.mostCommonTimeEfficient(new int[]{2,2,1,1,2});
+      System.out.println("Test 2: " + (result2 == 2 ? "PASSED" : "FAILED"));
+      
+      
+      int result3 = Practice.mostCommonTimeEfficient(new int[]{1,2,3});
+      System.out.println("Test 3: " + (result3 == 1 ? "PASSED" : "FAILED"));
+  }
+
+  public static void testMostCommonSpaceEfficient() {
+    
+    int result1 = Practice.mostCommonSpaceEfficient(new int[]{5});
+    System.out.println("Test 1 (Single element): " + (result1 == 5 ? "PASSED" : "FAILED"));
 
-  // Hints: They are static methods, so you will use the full Practice.mostCommonTimeEfficient for method calls
+    
+    int result2 = Practice.mostCommonSpaceEfficient(new int[]{1, 2, 2, 3, 3, 3});
+    System.out.println("Test 2 (Clear majority): " + (result2 == 3 ? "PASSED" : "FAILED"));
+
+  
+    int result3 = Practice.mostCommonSpaceEfficient(new int[]{1, 2, 2, 1});
+    System.out.println("Test 3 (Tie breaker): " + (result3 == 1 ? "PASSED" : "FAILED"));
 }
+}
\ No newline at end of file
diff --git a/src/tests.java b/src/tests.java
new file mode 100644
index 0000000..f11fb18
--- /dev/null
+++ b/src/tests.java
@@ -0,0 +1,52 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+public class tests {
+
+    @Test
+    public void testMostCommonTimeEfficient_SingleElement() {
+        int[] nums = {5};
+        assertEquals(5, Practice.mostCommonTimeEfficient(nums));
+    }
+
+    @Test
+    public void testMostCommonTimeEfficient_AllSameElements() {
+        int[] nums = {2, 2, 2, 2};
+        assertEquals(2, Practice.mostCommonTimeEfficient(nums));
+    }
+
+    @Test
+    public void testMostCommonTimeEfficient_OneMostCommon() {
+        int[] nums = {1, 2, 2, 3, 3, 3, 4};
+        assertEquals(3, Practice.mostCommonTimeEfficient(nums));
+    }
+
+    @Test
+    public void testMostCommonTimeEfficient_TieBreakerFirstWins() {
+        int[] nums = {1, 2, 2, 1, 1, 2, 3};
+        assertEquals(1, Practice.mostCommonTimeEfficient(nums));
+    }
+
+    @Test
+    public void mostCommonSpaceEfficient_mixedNums() {
+        int[] arr = {1, 2, 3, 4, 3, 4, 4};
+        int actual = Practice.mostCommonSpaceEfficient(arr);
+        assertEquals(4, actual);
+    }
+
+    @Test
+    public void mostCommonSpaceEfficient_tie() {
+        int[] arr = {1, 2, 2, 3, 4, 4};
+        int actual = Practice.mostCommonSpaceEfficient(arr);
+        assertEquals(2, actual);
+    }
+
+    @Test
+    public void mostCommonSpaceEfficient_noDups() {
+        int[] arr = {1, 2, 3, 4};
+        int actual = Practice.mostCommonSpaceEfficient(arr);
+        assertEquals(1, actual);
+    }
+
+    // Hints: They are static methods, so you will use the full Practice.mostCommonTimeEfficient for method calls
+}
\ No newline at end of file