Update EggDropping.java

src/main/java/com/thealgorithms/dynamicprogramming/EggDropping.java

@@ -1,51 +1,101 @@
 package com.thealgorithms.dynamicprogramming;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
 /**
- * DynamicProgramming solution for the Egg Dropping Puzzle
+ * Dynamic Programming solution for the Egg Dropping Puzzle
+ * The problem is to find the minimum number of attempts needed in the worst case to find the critical
+ * floor from which if an egg is dropped, it will break.
+ * Time Complexity: O(n * m * m), where n is number of eggs and m is number of floors
+ * Space Complexity: O(n * m) to store the DP table
+ * co-author @manishraj27
  */
 public final class EggDropping {
+
     private EggDropping() {
+        // private constructor to prevent instantiation
     }
 
-    // min trials with n eggs and m floors
-    public static int minTrials(int n, int m) {
-        int[][] eggFloor = new int[n + 1][m + 1];
-        int result;
-        int x;
+    /**
+     * Finds minimum number of trials needed in worst case for n eggs and m floors
+     *
+     * @param eggs The number of eggs available
+     * @param floors The number of floors in the building
+     * @return Minimum number of trials needed in worst case
+     * @throws IllegalArgumentException if eggs <= 0 or floors < 0
+     */
+    public static int minTrials(int eggs, int floors) {
+        if (eggs <= 0 || floors < 0) {
+            throw new IllegalArgumentException("Number of eggs must be positive and floors must be non-negative");
+        }
 
-        for (int i = 1; i <= n; i++) {
-            eggFloor[i][0] = 0; // Zero trial for zero floor.
-            eggFloor[i][1] = 1; // One trial for one floor
+        // dp[i][j] represents minimum number of trials needed for i eggs and j floors
+        int[][] dp = new int[eggs + 1][floors + 1];
+
+        // Base case 1: Zero trials for zero floor
+        // Base case 2: One trial for one floor
+        for (int i = 1; i <= eggs; i++) {
+            dp[i][0] = 0;
+            dp[i][1] = 1;
         }
 
-        // j trials for only 1 egg
-        for (int j = 1; j <= m; j++) {
-            eggFloor[1][j] = j;
+        // Base case 3: With one egg, need to try every floor from bottom
+        for (int j = 1; j <= floors; j++) {
+            dp[1][j] = j;
         }
 
-        // Using bottom-up approach in DP
-        for (int i = 2; i <= n; i++) {
-            for (int j = 2; j <= m; j++) {
-                eggFloor[i][j] = Integer.MAX_VALUE;
-                for (x = 1; x <= j; x++) {
-                    result = 1 + Math.max(eggFloor[i - 1][x - 1], eggFloor[i][j - x]);
-
-                    // choose min of all values for particular x
-                    if (result < eggFloor[i][j]) {
-                        eggFloor[i][j] = result;
-                    }
+        // Fill rest of the entries in table using optimal substructure property
+        for (int i = 2; i <= eggs; i++) {
+            for (int j = 2; j <= floors; j++) {
+                dp[i][j] = Integer.MAX_VALUE;
+                // Try dropping egg from each floor and find minimum trials needed
+                for (int k = 1; k <= j; k++) {
+                    // Maximum of:
+                    // 1) Egg breaks at floor k: Check below floors with i-1 eggs
+                    // 2) Egg doesn't break: Check above floors with i eggs
+                    int attempts = 1 + Math.max(dp[i - 1][k - 1], dp[i][j - k]);
+                    dp[i][j] = Math.min(dp[i][j], attempts);
                 }
             }
         }
 
-        return eggFloor[n][m];
+        return dp[eggs][floors];
+    }
+
+    @Test
+    void testBasicScenarios() {
+        // Test with 2 eggs and 4 floors
+        assertEquals(3, minTrials(2, 4));
+
+        // Test with 3 eggs and 5 floors
+        assertEquals(3, minTrials(3, 5));
+    }
+
+    @Test
+    void testEdgeCases() {
+        // Test with single egg
+        assertEquals(0, minTrials(1, 0));
+        assertEquals(1, minTrials(1, 1));
+        assertEquals(2, minTrials(1, 2));
+
+        // Test with multiple eggs but minimal floors
+        assertEquals(0, minTrials(2, 0));
+        assertEquals(1, minTrials(3, 1));
+    }
+
+    @Test
+    void testLargeInputs() {
+        assertEquals(4, minTrials(3, 10));
+        assertEquals(7, minTrials(2, 36));
     }
 
-    public static void main(String[] args) {
-        int n = 2;
-        int m = 4;
-        // result outputs min no. of trials in worst case for n eggs and m floors
-        int result = minTrials(n, m);
-        System.out.println(result);
+    @Test
+    void testInvalidInputs() {
+        assertThrows(IllegalArgumentException.class, () -> minTrials(0, 5));
+        assertThrows(IllegalArgumentException.class, () -> minTrials(-1, 5));
+        assertThrows(IllegalArgumentException.class, () -> minTrials(2, -1));
     }
 }