arrays - c# recursive step method -

i'm trying make recursive method check if last number (always 0) in integer array (with > 0 integers) reachable increasing (or decreasing) index of array value of array element of current index, while staying within bounds of array.

example:

say have following array, , start index == 0:

int[] arr = {3, 6, 4, 1, 3, 4, 2, 5, 3, 0}; 

step 0 : index = 0, value = 3

step 1 : index = 3, value = 1

step 2 : index = 4, value = 3

step 3 : index = 7, value = 5

step 4 : index = 2, value = 4

step 5 : index = 6, value = 2

step 6 : index = 8, value = 3

step 7 : index = 5, value = 4

step 8 : index = 9, value = 0 -- end

my current code:

        static bool solveable(int index, int[] arr)         {             if (arr[index] == 0)                 return true;             if (index + arr[index] < arr.length)                 return solveable(index + arr[index], arr);             if (index - arr[index] >= 0)                 return solveable(index - arr[index], arr);              return false;         } 

the thing work solveable cases, other cases result in stackoverflow exception.

how able solve problem without using global variables store previous results?

edit:

i can use parameters: (int index, int[] arr)

you correct stack overflow unsolvable cases: recursive code behave dog chasing own tail until, until reaches stack limit.

fortunately, can break infinite recursion observing have @ n steps reach end of array, if reach @ all. therefore, add third parameter indicate how many steps have taken already. if reach 0 before number of steps passes n, have path; otherwise, don't have path.

static bool solveable(int index, int[] arr, int stepssofar) {     if (arr[index] == 0)         return true;     if (stepssofar > arr.length)         return false;     ...     // rest of code; pass stepssofar+1 down next level } 

i can use 2 parameters included in code snippet

you can mark indexes have visited in arr placing -1 them. in order preserve array's original state, store old value in local variable, , set arr before returning:

static bool solveable(int index, int[] arr) {     if (arr[index] == 0)         return true;     if (arr[index] == -1)         return false;     int oldarratindex = arr[index];     arr[index] = -1;     try {         ...         // rest of code     } {         arr[index] = oldarratindex;     } }