solve issue #86

src/main/java/com/williamfiset/algorithms/datastructures/suffixarray/SuffixArrayNew.java

@@ -0,0 +1,103 @@
+package com.williamfiset.algorithms.datastructures.suffixarray;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class SuffixArrayNew {
+    public static final int SIZE = 256;
+
+    //generate SA list for String S
+    public static int[] generateSA(String s) {
+        //ch for CharArray
+        char[] ch = s.toCharArray();
+        int len = ch.length;
+        int m = SIZE;
+        /**
+         * sa store sa list
+         * x and y for temp using
+         */
+        int[] sa = new int[len];
+        int[] x = new int[len];
+        int[] y = new int[len];
+        int[] ysort = new int[len];
+        int[] bucket = new int[SIZE];
+
+        Arrays.fill(bucket, 0);
+        for (int i = 0; i < len; i++) {
+            x[i] = ch[i];
+            bucket[ch[i]]++;
+        }
+        for (int i = 1; i < m; i++)
+            bucket[i] += bucket[i-1];
+        for (int i = len-1; i >= 0; i--)
+            sa[--bucket[ch[i]]] = i;
+        //loops for sort and generate SA
+        for (int step = 1, p = 0; p < len; step *= 2, m = p) {
+            p = 0;
+            for (int i = len - step; i < len; i++)
+                y[p++] = i;
+            for (int i = 0; i < len; i++) {
+                if (sa[i] >= step)
+                    y[p++] = sa[i] - step;
+            }
+
+            for (int i = 0; i < len; i++)
+                ysort[i] = x[y[i]];
+
+            Arrays.fill(bucket, 0);
+            for (int i = 0; i < len; i++)
+                bucket[ysort[i]]++;
+            for (int i = 1; i < m; i++)
+                bucket[i] += bucket[i-1];
+            for (int i = len - 1; i >= 0; i--)
+                sa[--bucket[ysort[i]]] = y[i];
+
+            Arrays.fill(y, 0);
+            System.arraycopy(x, 0, y, 0, len);
+            //fill x
+            x[sa[0]] = 0;
+            p = 1;
+            for (int i = 1; i < len; i++)
+                x[sa[i]] = compare(y, sa[i], sa[i-1], step) ? p-1 : p++;
+        }
+        return sa;
+    }
+
+    public static int[] generateRank(int[] sa) {
+        int len = sa.length;
+        int[] rank = new int[len];
+        for (int i = 0; i < len; i++)
+            rank[sa[i]] = i;
+        return rank;
+    }
+
+
+
+    private static boolean inBounds(int i, int j, int len) {
+        return i < len && j < len;
+    }
+    //compare int and int list
+    private static boolean compare(int[] y, int a, int b, int l) {
+        int[] tmp = new int[y.length + 1];
+        System.arraycopy(y, 0, tmp, 0, y.length);
+        return tmp[a] == tmp[b] && tmp[a+l] == tmp[b+l];
+    }
+
+    public static void main(String[] args) {
+        System.out.println("Input the string: ");
+        String s="";
+        Scanner scan = new Scanner(System.in);
+        if (scan.hasNextLine()) {
+            s = scan.nextLine();
+        }
+        scan.close();
+        int[] sa = generateSA(s);
+        int[] rank = generateRank(sa);
+        System.out.println("sa   : " + Arrays.toString(sa));
+        System.out.println("ranked sa  : " + Arrays.toString(rank));
+        System.out.print("Each elements in sa represent: ");
+        for (int i = 0; i < sa.length; i++)
+            System.out.print(s.substring(sa[i])+" ");
+    }
+
+}

src/test/java/com/williamfiset/algorithms/datastructures/suffixarray/SuffixArrayNewTest.java

@@ -0,0 +1,40 @@
+package com.williamfiset.algorithms.datastructures.suffixarray;
+import static com.google.common.truth.Truth.assertThat;
+
+import java.security.SecureRandom;
+import java.util.Random;
+import org.junit.*;
+public class SuffixArrayNewTest {
+    @Test
+    public void suffixArrayLength(){
+        String str = "banana";
+
+        SuffixArrayNew saTest1=new SuffixArrayNew();
+        int[] result1= saTest1.generateSA(str);
+        assertThat(result1.length).isEqualTo(str.length());
+    }
+
+    @Test
+    public void suffixArrayTest1(){
+        String str = "banana";
+        int[] rightResult = {5,3,1,0,4,2};
+        SuffixArrayNew saTest2=new SuffixArrayNew();
+        int[] result2= saTest2.generateSA(str);
+        for(int i=0; i<rightResult.length;i++){
+            assertThat(result2[i]).isEqualTo(result2[i]);
+        }
+
+    }
+
+    @Test
+    public void suffixArrayTest2(){
+        String str = "WorldIsBigAndWeAreSmall";
+        int[] rightResult = {10, 15, 7, 5, 18, 13, 0, 20, 4, 12, 14, 17, 9, 8, 22, 3, 21, 19, 11, 1, 16, 2, 6};
+        SuffixArrayNew saTest2=new SuffixArrayNew();
+        int[] result2= saTest2.generateSA(str);
+        for(int i=0; i<rightResult.length;i++){
+            assertThat(result2[i]).isEqualTo(result2[i]);
+        }
+
+    }
+}