add s09

tp-algo2/src/s09/StringSearching.java

+package s09;
+
+// ------------------------------------------------------------ 
+public class StringSearching {
+  // ------------------------------------------------------------ 
+  static /*final*/ int HASHER = 301; // Maybe also try with 7 and 46237
+  static /*final*/ int BASE   = 256; // Please also try with 257
+  // ---------------------
+  static int firstFootprint(String s, int len) {
+    return -1;
+    // TODO - A COMPLETER
+  }
+  // ---------------------
+  // must absolutely be O(1)
+  // coef is (BASE  power  P.LENGTH-1)  mod  HASHER
+  static int nextFootprint(int previousFootprint, char dropChar, char newChar, int coef) {
+    return -1;
+    // TODO - A COMPLETER
+    // h = previousFootprint
+    // h = h - ...               // dropChar        (bien réfléchir !)
+    // h = h * ...               // shift
+    // h = h + ...               // newChar
+  }
+  // ---------------------
+  // Rabin-Karp algorithm
+  public static int indexOf_rk(String t, String p) {
+    return -1;
+    // TODO - A COMPLETER
+  }
+}

tp-algo2/src/s09/StringSearchingTestJU.java

+package s09;
+import org.junit.jupiter.api.Test;
+
+import java.util.Random;
+
+import static org.junit.jupiter.api.Assertions.*;
+// ------------------------------------------------------------ 
+public class StringSearchingTestJU {
+
+  // ------------------------------------------------------------ 
+  @Test
+  public void testRabinKarpHasher301Base256() {
+    System.out.println(" --- Trying with original HASHER and BASE...");
+    StringSearching.HASHER = 301;
+    StringSearching.BASE = 256;
+    int max = 400;
+    test(max);
+  }
+  @org.junit.jupiter.api.Test
+  public void testRabinKarpHasher7Base257() {
+    System.out.println(" --- Trying with another HASHER and BASE...");
+    StringSearching.HASHER = 77;
+    StringSearching.BASE  = 257;
+    int max = 400;
+    test(max);
+  }
+  // ------------------------------------------------------------ 
+  public static String rndWord(int length, String alphabet, Random r) {
+    String s="";
+    int x;
+    for (int i=0; i<length; i++) {
+      x = r.nextInt(alphabet.length());
+      s += alphabet.charAt(x);
+    }
+    return s;
+  }
+  // ------------------------------------------------------------ 
+  private static void test(int n) {
+    Random r = new Random();
+    String t, p;
+    int j;
+    int occ = 0;
+    String alphabet = "ab";
+    assertTrue( 0==StringSearching.indexOf_rk("wxyz", "wxyz"));
+    assertTrue(10==StringSearching.indexOf_rk("0123456789wxyz", "wxyz"));
+    assertTrue( 0==StringSearching.indexOf_rk("wxyz0123456789wxya", "wxyz"));
+    assertTrue(-1==StringSearching.indexOf_rk("wxyz0123456789wxywxyz0123456789wxy", "a"));
+    t = rndWord(n, alphabet, r);
+    for (int i=0; i<n*n; i++) {
+      int l = (int) Math.sqrt(n);
+      p = rndWord(1+r.nextInt(l), alphabet, r);
+      j = t.indexOf(p);
+      if (j!=-1) occ++;
+      assertTrue(j == StringSearching.indexOf_rk(t, p));
+    }
+    System.out.println("Nb of method calls : "+n*n);
+    System.out.println("Nb of found occurrences : "+occ);
+    System.out.println("Test passed successfully");
+  }
+  // ------------------------------------------------------------ 
+}