CODEWITHSUNDEEP
javaalgorithmbacktrackinglisrecursive-backtracking
Yurish
Yurish

Reputation: 29

finding all possible longest increasing subsequence using recursion

I tried to find all possible longest increasing subsequence using recursion. When I tried an input array {10,22,9,33,21,50,41,40,60,55}, it worked and the output was:

10 22 33 40 55 /
10 22 33 41 55 /
10 22 33 50 55 /
10 22 33 40 60 /
10 22 33 41 60 /
10 22 33 50 60 /

But when I tried an input array {2,-3,4,90,-2,-1,-10,-9,-8}, I got an output:

-3 4 90 /
-3 -2 -1 /
-10 -9 -8 /

In this case I didn't get 2 4 90. What should I change in my code to make it word for this case?

public class Main {
    public static void main(String[] args) {
        int arr[]={10,22,9,33,21,50,41,40,60,55};
        int lis[]=new int[arr.length];
        for(int i=0;i<arr.length;i++){
            lis[i]=1;
        }
        for(int i=1;i<arr.length;i++){
            for(int j=0;j<i;j++){
                if(arr[i]>arr[j]&&lis[i]<lis[j]+1){
                    lis[i]=lis[j]+1;
                }
            }
        }
        int max=0;
        for(int i=0;i<arr.length;i++){
            if(max<lis[i])
                max=lis[i];
        }
        //**************Recursive Print LIS****************
        int rIndex=-1;
        for(int i=arr.length-1;i>=0;i--){
            if(lis[i]==max){
                 rIndex=i;
                 break;
            }
        }
        int res[]=new int[max];
        printLISRecursive(arr,rIndex,lis,res,max,max);
    }

    private static void printLISRecursive(int[] arr, int maxIndex, int[] lis, int[] res, int i, int max) {
        if(maxIndex<0)return;
        if(max==1&&lis[maxIndex]==1&&i==1){
            res[i-1]=arr[maxIndex];
//            System.out.println("Using Print Recursion:");
            for(int j=0;j<res.length;j++){
                System.out.print(res[j]+" ");
            }
            System.out.println();
            return;
        }
        if(lis[maxIndex]==max){
            res[i-1]=arr[maxIndex];
            printLISRecursive(arr, maxIndex-1, lis, res, i-1, max-1);
        }
        printLISRecursive(arr, maxIndex-1, lis, res, i, max);
    }

}

Upvotes: 3

Views: 6214

Answers (2)

Tharindu Kumara
Tharindu Kumara

Reputation: 4458

public static String  lcs(String  a, String  b){
    int aLen = a.length();
    int bLen = b.length();
    if(aLen == 0 || bLen == 0){
        return "";
    }else if(a.charAt(aLen-1) == b.charAt(bLen-1)){
        return lcs(a.substring(0,aLen-1),b.substring(0,bLen-1))
            + a.charAt(aLen-1);
    }else{
        String  x = lcs(a, b.substring(0,bLen-1));
        String  y = lcs(a.substring(0,aLen-1), b);
        return (x.length() > y.length()) ? x : y;
    }
}

Upvotes: 2

Tharindu Kumara
Tharindu Kumara

Reputation: 4458

public static int lcsrec(String x, String y) {

    // If one of the strings has one character, search for that character
    // in the other string and return the appropriate answer.
    if (x.length() == 1) 
      return find(x.charAt(0), y);
    if (y.length() == 1)
      return find(y.charAt(0), x);

    // Solve the problem recursively.

    // Corresponding beginning characters match.
    if (x.charAt(0) == y.charAt(0))
      return 1+lcsrec(x.substring(1), y.substring(1));

    // Corresponding characters do not match.
    else 
      return max(lcsrec(x,y.substring(1)), lcsrec(x.substring(1),y));

  }

Upvotes: 1

Related Questions