Sudoku Function returning array of identical boards - objective-c

Question

I am writing a recursive Sudoku solver and I am having some issues with 2D array handling. I included the function which is giving the trouble. There are some unnecessary lines I was using for debugging in there.
- (Stack *)successors
{
Stack *stack = [[Stack alloc] init];
NSMutableArray *temp = [[NSMutableArray alloc] init];
NSMutableArray *test = [[NSMutableArray alloc] init];
temp = [self.board copy];
for (int x = 0; x < columns; x++) {
for (int y = 0; y < rows; y++) {
if ([self.board[x][y] isEqualToString:#""] ||
[self.board[x][y] isEqualToString:#"."]) {
NSLog(#"%d %d", x, y);
for (int i = 1; i < 10; i++) {
NSLog(#"%d", i);
[temp[x] setObject:[NSString stringWithFormat:#"%d", i] atIndex:y];
State *tempState = [[State alloc] initWithBoard:temp];
if ([tempState legal]) {
NSMutableArray *input = [NSMutableArray arrayWithArray:temp];
[stack push:input];
[stack push:input];
[test addObject:input];
}
}
NSLog(#"test %#", test);
int p = [stack size];
for (int i = 0; i < p; i++) {
NSLog(#"%#", [stack pop]);
}
return stack;
}
}
}
return stack;
}
essentially, it begins at the top of the array and if the space is empty, it tries putting in the number 1 through 9 and if it is legal, based on another function I wrote previously, it will input it in the temp array and add it to the stack. I checked this and it works great. However, after adding them all together, I NSLog to check the stack and find that all of the stacked arrays now begin with the number 9, the last number checked in the temp array. I believe I am having some issue with keeping reference to the temp array, but I cannot figure it out. Any help is great.