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Tail Recursion Experiments in Objective-C
//
// Created by Jonathon Mah on 2014-05-24.
// Released into the public domain.
//
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
@interface ListNode : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, strong) ListNode *next;
- (NSUInteger)length_v1;
- (NSUInteger)length_v2;
- (NSUInteger)length_v3;
- (NSUInteger)length_v4;
- (NSUInteger)length_v5;
- (NSUInteger)length_v6;
- (NSUInteger)length_v7;
- (NSUInteger)length_v8;
@end
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSArray *names = @[@"Jack", @"Jill", @"Alice", @"Bob", @"Eve"];
ListNode *head = nil;
for (NSUInteger i = 0; i < 10; i++) {
ListNode *ln = [ListNode new];
ln.name = names[arc4random_uniform((uint32_t)names.count)];
ln.next = head;
head = ln;
}
NSLog(@"length: %lu", head.length_v1);
NSLog(@"length: %lu", head.length_v2);
NSLog(@"length: %lu", head.length_v3);
NSLog(@"length: %lu", head.length_v4);
NSLog(@"length: %lu", head.length_v5);
NSLog(@"length: %lu", head.length_v6);
NSLog(@"length: %lu", head.length_v7);
NSLog(@"length: %lu", head.length_v8);
}
return 0;
}
@implementation ListNode
- (NSUInteger)length_v1 {
return 1 + [self.next length_v1];
}
- (NSUInteger)length_v2 {
return [[self class] lengthOfListWithHead_v2:self];
}
+ (NSUInteger)lengthOfListWithHead_v2:(ListNode *)node {
if (!node)
return 0; // base case
else
return 1 + [self lengthOfListWithHead_v2:node.next];
}
- (NSUInteger)length_v3 {
return [[self class] lengthOfListWithHead_v3:self];
}
+ (NSUInteger)lengthOfListWithHead_v3:(ListNode *)node {
NSUInteger count = 0;
while (node) {
count += 1;
node = node.next;
}
return count;
}
- (NSUInteger)length_v4 {
return [[self class] lengthOfListWithHead_v4:self count:0];
}
+ (NSUInteger)lengthOfListWithHead_v4:(ListNode *)node count:(NSUInteger)count {
while (node) {
count += 1;
node = node.next;
}
return count;
}
- (NSUInteger)length_v5 {
return [[self class] lengthOfListWithHead_v5:self count:0];
}
+ (NSUInteger)lengthOfListWithHead_v5:(ListNode *)node count:(NSUInteger)count {
top:
if (!node) {
return count;
} else {
count += 1;
node = node.next;
goto top;
}
}
- (NSUInteger)length_v6 {
return [[self class] lengthOfListWithHead_v6:self count:0];
}
+ (NSUInteger)lengthOfListWithHead_v6:(ListNode *)node count:(NSUInteger)count {
if (!node)
return count;
else {
return [self lengthOfListWithHead_v6:node.next count:(count + 1)];
}
}
- (NSUInteger)length_v7 {
return [[self class] lengthOfListWithHead_v7:self count:0];
}
+ (NSUInteger)lengthOfListWithHead_v7:(ListNode *)node count:(NSUInteger)count {
if (!node)
return count;
else
return [self lengthOfListWithHead_v7:node->_next count:(count + 1)];
}
- (NSUInteger)length_v8 {
return [[self class] lengthOfListWithHead_v8:self count:0];
}
+ (NSUInteger)lengthOfListWithHead_v8:(ListNode *)node count:(NSUInteger)count {
if (!node)
return count;
else if ([node isMemberOfClass:self])
return [self lengthOfListWithHead_v8:node->_next count:(count + 1)];
else
return [self lengthOfListWithHead_v8:node.next count:(count + 1)];
}
@end
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