create DistinctSubsequenceOccurrenceCount.java

Author: vikasjindalVJL

String/Substring/DistinctSubsequenceOccurrenceCount.java

@@ -0,0 +1,60 @@
+import java.io.*; 
+  
+class DistinctSubsequenceOccurrenceCount { 
+    static int findSubsequenceCount(String S, String T) 
+    { 
+        int m = T.length(); 
+        int n = S.length(); 
+  
+        // T can't appear as a subsequence in S 
+        if (m > n) 
+            return 0; 
+  
+        // mat[i][j] stores the count of 
+        // occurrences of T(1..i) in S(1..j). 
+        int mat[][] = new int[m + 1][n + 1]; 
+  
+        // Initializing first column with 
+        // all 0s. An emptystring can't have 
+        // another string as suhsequence 
+        for (int i = 1; i <= m; i++) 
+            mat[i][0] = 0; 
+  
+        // Initializing first row with all 1s. 
+        // An empty string is subsequence of all. 
+        for (int j = 0; j <= n; j++) 
+            mat[0][j] = 1; 
+  
+        // Fill mat[][] in bottom up manner 
+        for (int i = 1; i <= m; i++) { 
+            for (int j = 1; j <= n; j++) { 
+                // If last characters don't match, 
+                // then value is same as the value 
+                // without last character in S. 
+                if (T.charAt(i - 1) != S.charAt(j - 1)) 
+                    mat[i][j] = mat[i][j - 1]; 
+  
+                // Else value is obtained considering two cases. 
+                // a) All substrings without last character in S 
+                // b) All substrings without last characters in 
+                // both. 
+                else
+                    mat[i][j] = mat[i][j - 1] + mat[i - 1][j - 1]; 
+            } 
+        } 
+  
+        /* uncomment this to print matrix mat 
+        for (int i = 1; i <= m; i++, cout << endl) 
+            for (int j = 1; j <= n; j++) 
+                System.out.println ( mat[i][j] +" "); */
+        return mat[m][n]; 
+    } 
+  
+    // Driver code to check above method 
+    public static void main(String[] args) 
+    { 
+        String T = "ge"; 
+        String S = "geeksforgeeks"; 
+        System.out.println(findSubsequenceCount(S, T)); 
+    } 
+}