Added a new code for finding largest date and time from given digits

Author: Rishav123raj

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

@@ -0,0 +1,113 @@
+package com.thealgorithms.backtracking;
+
+import java.util.*;
+
+public class LargestValidDateTimefromDigits {
+    public static void main(String args[]) {
+        Scanner sc = new Scanner(System.in);
+        String input = sc.nextLine();
+        String parts[] = input.split(",");
+        List<Integer> digits = new ArrayList<>();
+        for (String part : parts) {
+            digits.add(Integer.parseInt(part));
+        }
+        Collections.sort(digits, Collections.reverseOrder());
+        String result = findLargestValidDateTime(digits);
+        System.out.println(result);
+    }
+
+    // Function for latest valid Date Time
+    public static String findLargestValidDateTime(List<Integer> digits) {
+        List<Integer> month = findValidMonth(digits);
+        if (month == null)
+            return "0"; // No valid month
+
+        List<Integer> day = findValidDay(digits, month);
+        if (day == null)
+            return "0"; // No valid day
+
+        List<Integer> hour = findValidHour(digits, month, day);
+        if (hour == null)
+            return "0"; // No valid hour
+
+        List<Integer> minute = findValidMinute(digits, month, day, hour);
+        if (minute == null)
+            return "0"; // No valid minute
+
+        // Format the result: MM/DD HH:MM
+        return String.format("%02d/%02d %02d:%02d",
+                month.get(0) * 10 + month.get(1),
+                day.get(0) * 10 + day.get(1),
+                hour.get(0) * 10 + hour.get(1),
+                minute.get(0) * 10 + minute.get(1));
+    }
+
+    // Function for Valid Month
+    public static List<Integer> findValidMonth(List<Integer> digits) {
+        for (int i = 0; i < digits.size(); i++) {
+            for (int j = 0; j < digits.size(); j++) {
+                if (i != j) {
+                    int month = digits.get(i) * 10 + digits.get(j);
+                    if (month >= 1 && month <= 12) {
+                        return Arrays.asList(digits.remove(i), digits.remove(j > i ? j - 1 : j));
+                    }
+                }
+            }
+        }
+        return null; // No valid month found
+    }
+
+    // Function for Valid Day
+    public static List<Integer> findValidDay(List<Integer> digits, List<Integer> month) {
+        int maxDay = getMaxDays(month.get(0) * 10 + month.get(1)); // Get the max days of the selected month
+        for (int i = 0; i < digits.size(); i++) {
+            for (int j = 0; j < digits.size(); j++) {
+                if (i != j) {
+                    int day = digits.get(i) * 10 + digits.get(j);
+                    if (day >= 1 && day <= maxDay) {
+                        return Arrays.asList(digits.remove(i), digits.remove(j > i ? j - 1 : j));
+                    }
+                }
+            }
+        }
+        return null; // No valid day found
+    }
+
+    // Function for Valid Hour
+    public static List<Integer> findValidHour(List<Integer> digits, List<Integer> month, List<Integer> day) {
+        for (int i = 0; i < digits.size(); i++) {
+            for (int j = 0; j < digits.size(); j++) {
+                if (i != j) {
+                    int hour = digits.get(i) * 10 + digits.get(j);
+                    if (hour >= 0 && hour <= 23) {
+                        return Arrays.asList(digits.remove(i), digits.remove(j > i ? j - 1 : j));
+                    }
+                }
+            }
+        }
+        return null; // No valid hour found
+    }
+
+    // Function for Valid Minute
+    public static List<Integer> findValidMinute(List<Integer> digits, List<Integer> month, List<Integer> day,
+            List<Integer> hour) {
+        for (int i = 0; i < digits.size(); i++) {
+            for (int j = 0; j < digits.size(); j++) {
+                if (i != j) {
+                    int minute = digits.get(i) * 10 + digits.get(j);
+                    if (minute >= 0 && minute <= 59) {
+                        return Arrays.asList(digits.get(i), digits.get(j));
+                    }
+                }
+            }
+        }
+        return null; // No valid minute found
+    }
+
+    // Function for maximum days in a month
+    public static int getMaxDays(int month) {
+        // Max days in each month (index 0 = January)
+        int[] maxDaysInMonth = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+        return maxDaysInMonth[month - 1];
+    }
+}

src/test/java/com/thealgorithms/backtracking/LargestValidDateTimefromDigitsTest.java

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+package com.thealgorithms.backtracking;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class LargestValidDateTimefromDigitsTest {
+    @Test
+    public void testLargestValidDateTime() {
+        // Test case 1: All digits can form a valid date and time
+        List<Integer> digits1 = Arrays.asList(2, 0, 2, 1, 1, 2, 3, 4); // Example: 12/31 23:42
+        String expected1 = "12/31 23:42";
+        String result1 = LargestValidDateTimefromDigits.findLargestValidDateTime(digits1);
+        assertEquals(expected1, result1);
+
+        // Test case 2: No valid date can be formed (invalid month)
+        List<Integer> digits2 = Arrays.asList(4, 5, 6, 7, 8, 9); // No valid month can be formed
+        String expected2 = "0"; // No valid datetime
+        String result2 = LargestValidDateTimefromDigits.findLargestValidDateTime(digits2);
+        assertEquals(expected2, result2);
+
+        // Test case 3: Valid month but invalid day
+        List<Integer> digits3 = Arrays.asList(1, 2, 3, 4, 7, 9); // Valid month, but day > 31
+        String expected3 = "0"; // No valid datetime
+        String result3 = LargestValidDateTimefromDigits.findLargestValidDateTime(digits3);
+        assertEquals(expected3, result3);
+
+        // Test case 4: Valid datetime with unused digits
+        List<Integer> digits4 = Arrays.asList(2, 0, 2, 1, 1, 9, 5, 6); // Example: 12/19 21:50
+        String expected4 = "12/19 21:50";
+        String result4 = LargestValidDateTimefromDigits.findLargestValidDateTime(digits4);
+        assertEquals(expected4, result4);
+    }
+}