How to reverse single link list , using Objective C - objective-c

Question

I write a single link list , but don't know how to reverse , this is my some code.
node class MMNode
#import <Foundation/Foundation.h>
#interface MMNode : NSObject
#property (nonatomic, assign) int data;//data
#property (nonatomic, strong) MMNode *next;//next node
#end
Single link list class MMList
#import <Foundation/Foundation.h>
#import "MMNode.h"
#interface MMList : NSObject
#property (nonatomic, strong) MMNode *head;//first node
#property (nonatomic, strong) MMNode *hail;//last node
//init
- (instancetype)initWithData:(int)data;
//append
- (void)append:(int)data;
//print
- (void)printList;
//
- (void)reverse;
#end
How to reverse single link list?
- (void)reverse {
//Code...?
}

Answer 1

I am posting my code, as I don't know what exactly you have implemented.
LinkNode.h
#import <Foundation/Foundation.h>
#interface LinkNode : NSObject
#property (nonatomic) int data;
#property (nonatomic) LinkNode *next;
-(id)initWithData:(int) data;
#end
LinkNode.m
#import "LinkNode.h"
#implementation LinkNode
-(id)initWithData:(int) data{
if (self = [super init]){
self.data = data;
self.next = nil;
}
return self;
}
#end
SinglyLinkedList.h
#import <Foundation/Foundation.h>
#import "LinkNode.h"
#interface SinglyLinkedList : NSObject
#property(nonatomic) LinkNode *head;
#property(nonatomic) LinkNode *current;
-(id) initWithCapacity: (int)capacity;
-(void) appendData:(int)data;
-(void) prependData : (int)data;
-(void) printList:(LinkNode*)node;
-(void) reverseList;
-(void) deleteData:(int)data;
#end
SinglyLinkedList.m
#import "SinglyLinkedList.h"
#import "LinkNode.h"
#interface SinglyLinkedList()
#end
#implementation SinglyLinkedList
-(id)initWithCapacity:(int)capacity{
if (self == [super init]) {
for (int i=1; i<=capacity;i++) {
[self appendData:i];
}
}
return self;
}
-(void) appendData:(int)data{
if (self.head == nil){
self.current = [[LinkNode alloc] initWithData:data];
self.head = self.current;
return;
}
while (self.current.next != nil) {
self.current = self.current.next;
}
self.current.next = [[LinkNode alloc] initWithData:data];
}
-(void)prependData:(int)data{
if (self.head == nil){
self.current = [[LinkNode alloc] initWithData:data];
self.head = self.current;
return;
}
self.current = [[LinkNode alloc] initWithData:data];
self.current.next = self.head;
self.head = self.current;
}
-(void) printList:(LinkNode *)node {
while (node != nil) {
NSLog(#" %d \t", node.data);
node = node.next;
}
}
-(void) reverseList {
LinkNode *prev = nil;
LinkNode *current = self.head;
LinkNode *next = nil;
while (current != nil) {
next = current.next;
current.next = prev;
prev = current;
current = next;
}
self.head = prev;
}
-(void)deleteData:(int)data{
if (self.head == nil) { return; }
if (self.head.data == data) {
self.head = self.head.next;
return;
}
LinkNode *currentNode = self.head;
while (currentNode.next != nil) {
if (currentNode.next.data == data){
currentNode.next = currentNode.next.next;
return;
}
currentNode = currentNode.next;
}
}
#end
Call from main.m
int main(int argc, const char * argv[]) {
SinglyLinkedList *list = [[SinglyLinkedList alloc] initWithCapacity:5];
[list appendData:15];
NSLog(#"After Append");
[list printList:list.head];
[list prependData:0];
NSLog(#"After Prepend");
[list printList:list.head];
[list reverseList];
NSLog(#"After Reverse");
[list printList:list.head];
[list deleteData:15];
[list reverseList];
NSLog(#"After Delete");
[list printList:list.head];
return NSApplicationMain(argc, argv);
}
For more understanding you can refer this link from geeksforgeeks