CODEWITHSUNDEEP
javaarraysrecursion
Erebus
Erebus

Reputation: 141

Java Lab - Counting Runs

Langauge: Java

No syntax errors and passed the compiler but failed my tester. Anyone can tell me what I did wrong here?

Here's what the lab text states for what the method is to do: "counts how many runs (consecutive blocks of equal elements) there are in the subarray of arr from index start to index end , inclusive"

Also: I'm not allowed to use any loops for this lab, if-else statements are okay though.

parameters: arr = array, start/end = indices for start/end

public class Recursion {
    int countRuns(int[] arr, int start, int end) {
        if (start >= end) 
            return 0; //checks for null arrays 

        int counter = 0; 
        if (start == 0)
            counter = 1; 

        //check the next element for similarity/difference 
        if (arr[start] != arr[start+1])
            counter = 1; 

        return counter + countRuns(arr, start + 1, end);  
    }
}

Upvotes: 0

Views: 416

Answers (1)

xs0
xs0

Reputation: 2897

I think you just slightly missed the conditions at beginning and end.. This should work:

public class Recursion {
    int countRuns(int[] arr, int start, int end) {
        if (start > end) 
            return 0; //checks for null arrays 

        if (start == end) // the indices are inclusive
            return 1;

        int counter; 
        if (arr[start] == arr[start + 1]) {
            counter = 0; // we'll still be in the same run, if they're equal
        } else {
            counter = 1; // otherwise it's a new run
        }

        return counter + countRuns(arr, start + 1, end);
    }
}

Upvotes: 3

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