Add chapter 22 23 24 25 answers

ch_22/Exercise22_04.java

@@ -4,7 +4,7 @@
 import java.util.Scanner;
 
 /**
- * (Pattern matching) Write a program that prompts the user to enter two strings
+ * *22.4 (Pattern matching) Write a program that prompts the user to enter two strings
  * and tests whether the second string is a substring of the first string. (Don’t use
  * the indexOf method in the String class.) Analyze the time complexity of
  * your algorithm. Here is a sample run of the program:

ch_22/Exercise22_05.java

@@ -0,0 +1,52 @@
+package ch_22;
+
+import java.util.Scanner;
+
+/**
+ * 22.5 (Same-number subsequence) Write an O(n) program that prompts the user to
+ * enter a sequence of integers ending with 0 and finds the longest subsequence
+ * with the same number. Here is a sample run of the program:
+ * Enter a series of numbers ending with 0:
+ * 2 4 4 8 8 8 8 2 4 4 0
+ * The longest same number sequence starts at index 3 with 4 values of 8
+ */
+public class Exercise22_05 {
+    private void findSubsequence(String[] tokens) {
+        int longest = 0;
+        int longestStartIndex = 0;
+        int count = 1;
+        int value = 0;
+        int startIndex = 0;
+
+        for (int i = 0; i < tokens.length - 1; i++) {
+            int curr = Integer.parseInt(tokens[i]);
+            int next = Integer.parseInt(tokens[i + 1]);
+            if (next == 0) break;
+            if (curr == next) {
+                count++;
+                longest = Math.max(longest, count);
+                if (count == longest) {
+                    value = curr;
+                    longestStartIndex = startIndex;
+                }
+            } else {
+                startIndex = i + 1;
+                count = 1;
+            }
+
+        }
+        System.out.println("The longest same number sequence starts at index " + longestStartIndex +
+                " with " + longest + " values " + "of " + value);
+
+    }
+
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
+        System.out.println("Enter a series of numbers ending with 0:");
+        String[] tokens = input.nextLine().split("\\s+");
+        new Exercise22_05().findSubsequence(tokens);
+
+        input.close();
+
+    }
+}