Count subsequence

#1


what is wrong in this code?

#2

your approach seems to be right

modulus is given
means ans can larger
so pls take long

#3

It is showing error ,i have changed long instead of int

#4

it is not passing the testcases

#5

pls see the changes which i have made
approach was right
just i have the int arry to long
and used the modulus oper

hope this will help u
pls rate my work
pls

import java.util.*;
public class Main {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);

	int t = sc.nextInt();
    sc.nextLine();
	long[] ans =new long[t];
	for(int i =0;i<t;i++) {
		String x = sc.nextLine();
		 long count = countSub(x);
		 ans[i]=count;
	}
	for(int i =0;i<t;i++) {
		System.out.println(ans[i]%1000000007);
	}
}
public static long countSub(String str) {
	
	 final int MAX_LENGTH=256;
	 int mod=1000000007;
	 int[] last = new int[MAX_LENGTH];
	 Arrays.fill(last, -1);
	 
	 int n = str.length();
	 
	 long[] dp = new long[n+1];
	 
	 dp[0]=1;
	 
	 for(int i =1;i<=n;i++) {
		 
		 dp[i] = (2*dp[i-1])%mod;
		 
		 
		 if(last[(int)str.charAt(i-1)]!= -1) {
			 dp[i] = (((dp[i] - dp[last[(int)str.charAt(i-1)]]))+mod)%mod;
		 }
		 
		 last[(int)str.charAt(i-1)]= i-1;
	 }
	 
	 return dp[n];
}

}

#6

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