add 3571

Author: fishercoder1534

paginated_contents/algorithms/4th_thousand/README.md

@@ -76,7 +76,8 @@
 | 3622 | [Check Divisibility by Digit Sum and Product](https://leetcode.com/problems/check-divisibility-by-digit-sum-and-product/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3622.java) |                                                                               | Easy       | 
 | 3608 | [Minimum Time for K Connected Components](https://leetcode.com/problems/minimum-time-for-k-connected-components/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3608.java) |                                                                               | Medium     | UnionFind
 | 3606 | [Coupon Code Validator](https://leetcode.com/problems/coupon-code-validator/)                                                               | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3606.java) |                                                                               | Easy       |
-| 3581 | [Count Odd Letters from Number](https://leetcode.com/problems/count-odd-letters-from-number/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3581.java) |                                                                               | Easy       | 
+| 3581 | [Count Odd Letters from Number](https://leetcode.com/problems/count-odd-letters-from-number/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3581.java) |                                                                               | Easy       |
+| 3571 | [Find the Shortest Superstring II](https://leetcode.com/problems/find-the-shortest-superstring-ii/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3571.java) |                                                                               | Easy       |
 | 3569 | [Count Islands With Total Value Divisible by K](https://leetcode.com/problems/count-islands-with-total-value-divisible-by-k/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3569.java) |                                                                               | Medium     | Union Find
 | 3550 | [Smallest Index With Digit Sum Equal to Index](https://leetcode.com/problems/smallest-index-with-digit-sum-equal-to-index/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3550.java) |                                                                               | Easy       |
 | 3545 | [Minimum Deletions for At Most K Distinct Characters](https://leetcode.com/problems/minimum-deletions-for-at-most-k-distinct-characters/)                                                              | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3545.java) |                                                                               | Easy       |

src/main/java/com/fishercoder/solutions/fourththousand/_3571.java

@@ -0,0 +1,48 @@
+package com.fishercoder.solutions.fourththousand;
+
+public class _3571 {
+    public static class Solution1 {
+        public String shortestSuperstring(String s1, String s2) {
+            String longer = s1.length() > s2.length() ? s1 : s2;
+            String shorter = longer.equals(s1) ? s2 : s1;
+            if (longer.indexOf(shorter) != -1) {
+                return longer;
+            }
+            //find the longest prefix of s1 that matches the longest suffix of s2
+            String candidate = "";
+            for (int i = s1.length(); i > 0; i--) {
+                String prefix = s1.substring(0, i);
+                for (int j = 0; j < s2.length(); j++) {
+                    String suffix = s2.substring(j);
+                    if (prefix.equals(suffix)) {
+                        candidate = s2 + s1.substring(i);
+                        break;
+                    }
+                }
+                if (!candidate.isEmpty()) {
+                    break;
+                }
+            }
+
+            //then do the other way:
+            for (int i = s2.length(); i > 0; i--) {
+                String prefix = s2.substring(0, i);
+                for (int j = 0; j < s1.length(); j++) {
+                    String suffix = s1.substring(j);
+                    if (prefix.equals(suffix)) {
+                        String candidate2 = s1 + s2.substring(i);
+                        if (candidate.isEmpty()) {
+                            return candidate2;
+                        }
+                        if (candidate2.length() < candidate.length()) {
+                            return candidate2;
+                        } else {
+                            return candidate;
+                        }
+                    }
+                }
+            }
+            return candidate.isEmpty() ? s1 + s2 : candidate;
+        }
+    }
+}

src/test/java/com/fishercoder/fourththousand/_3571Test.java

@@ -0,0 +1,37 @@
+package com.fishercoder.fourththousand;
+
+import com.fishercoder.solutions.fourththousand._3571;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class _3571Test {
+    private _3571.Solution1 solution1;
+
+    @BeforeEach
+    public void setup() {
+        solution1 = new _3571.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals("aaa", solution1.shortestSuperstring("aa", "aaa"));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals("tfj", solution1.shortestSuperstring("t", "fj"));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals("lkgy", solution1.shortestSuperstring("lk", "kgy"));
+    }
+
+    @Test
+    public void test4() {
+        assertEquals("baba", solution1.shortestSuperstring("aba", "bab"));
+    }
+
+}