链表（linked list）是一种物理存储单元上非连续、非顺序的存储结构，数据元素的逻辑顺序是通过链表中的指针链接次序实现的，表现形式如下图所示：
单链表
双链表
数组和链表区别：
- 数组：数组元素在内存上连续存放，可以通过下标查找元素；插入、删除需要移动大量元素，比较适用于元素很少变化的情况
- 链表：链表中的元素在内存中不是顺序存储的，查找慢，插入、删除只需要对元素指针重新赋值，效率高
objective-c 里没有现成的链表结构，下面我实现了非线程安全的单链表和双链表，以下都是具体的实现细节，完整代码可以在这儿下载
单链表
单链表提供了插入、删除、查询、反转等操作，具体实现如下：
bbsinglelinkedlist.h
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#import <foundation/foundation.h>@interface bbsinglelinkednode : nsobject <nscopying>@property (nonatomic, strong) nsstring *key;@property (nonatomic, strong) nsstring *value;@property (nonatomic, strong) bbsinglelinkednode *next;- (instancetype)initwithkey:(nsstring *)key value:(nsstring *)value;+ (instancetype)nodewithkey:(nsstring *)key value:(nsstring *)value;@end@interface bbsinglelinkedlist : nsobject- (void)insertnode:(bbsinglelinkednode *)node;- (void)insertnodeathead:(bbsinglelinkednode *)node;- (void)insertnode:(bbsinglelinkednode *)newnode beforenodeforkey:(nsstring *)key;- (void)insertnode:(bbsinglelinkednode *)newnode afternodeforkey:(nsstring *)key;- (void)bringnodetohead:(bbsinglelinkednode *)node;- (void)removenode:(bbsinglelinkednode *)node;- (bbsinglelinkednode *)nodeforkey:(nsstring *)key;- (bbsinglelinkednode *)headnode;- (bbsinglelinkednode *)lastnode;- (nsinteger)length;- (bool)isempty;- (void)reverse;- (void)readallnode;@end |
bbsinglelinkedlist.m
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#import "bbsinglelinkedlist.h"@implementation bbsinglelinkednode- (instancetype)initwithkey:(nsstring *)key value:(nsstring *)value{ if (self = [super init]) { _key = key; _value = value; } return self;}+ (instancetype)nodewithkey:(nsstring *)key value:(nsstring *)value{ return [[[self class] alloc] initwithkey:key value:value];}#pragma mark - nscopying- (id)copywithzone:(nullable nszone *)zone{ bbsinglelinkednode *newnode = [[bbsinglelinkednode allocwithzone:zone] init]; newnode.key = self.key; newnode.value = self.value; newnode.next = self.next; return newnode;}@end@interface bbsinglelinkedlist ()@property (nonatomic, strong) bbsinglelinkednode *headnode;@property (nonatomic, strong) nsmutabledictionary *innermap;@end@implementation bbsinglelinkedlist- (instancetype)init{ self = [super init]; if (self) { _innermap = [nsmutabledictionary new]; } return self;}#pragma mark - public- (void)insertnodeathead:(bbsinglelinkednode *)node{ if (!node || node.key.length == 0) { return; } if ([self isnodeexists:node]) { return; } _innermap[node.key] = node; if (_headnode) { node.next = _headnode; _headnode = node; } else { _headnode = node; }}- (void)insertnode:(bbsinglelinkednode *)node{ if (!node || node.key.length == 0) { return; } if ([self isnodeexists:node]) { return; } _innermap[node.key] = node; if (!_headnode) { _headnode = node; return; } bbsinglelinkednode *lastnode = [self lastnode]; lastnode.next = node;}- (void)insertnode:(bbsinglelinkednode *)newnode beforenodeforkey:(nsstring *)key{ if (key.length == 0 || !newnode || newnode.key.length == 0) { return; } if ([self isnodeexists:newnode]) { return; } if (!_headnode) { _headnode = newnode; return; } bbsinglelinkednode *node = _innermap[key]; if (node) { _innermap[newnode.key] = newnode; bbsinglelinkednode *aheadnode = [self nodebeforenode:node]; if (aheadnode) { aheadnode.next = newnode; newnode.next = node; } else { _headnode = newnode; newnode.next = node; } } else { [self insertnode:newnode]; //insert to tail }}- (void)insertnode:(bbsinglelinkednode *)newnode afternodeforkey:(nsstring *)key{ if (key.length == 0 || !newnode || newnode.key.length == 0) { return; } if ([self isnodeexists:newnode]) { return; } if (!_headnode) { _headnode = newnode; return; } bbsinglelinkednode *node = _innermap[key]; if (node) { _innermap[newnode.key] = newnode; newnode.next = node.next; node.next = newnode; } else { [self insertnode:newnode]; //insert to tail }}- (void)removenode:(bbsinglelinkednode *)node{ if (!node || node.key.length == 0) { return; } [_innermap removeobjectforkey:node.key]; if (node.next) { node.key = node.next.key; node.value = node.next.value; node.next = node.next.next; } else { bbsinglelinkednode *aheadnode = [self nodebeforenode:node]; aheadnode.next = nil; }}- (void)bringnodetohead:(bbsinglelinkednode *)node{ if (!node || !_headnode) { return; } if ([node isequal:_headnode]) { return; } bbsinglelinkednode *aheadnode = [self nodebeforenode:node]; aheadnode.next = node.next; node.next = _headnode; _headnode = node;}- (bbsinglelinkednode *)nodeforkey:(nsstring *)key{ if (key.length == 0) { return nil; } bbsinglelinkednode *node = _innermap[key]; return node;}- (bbsinglelinkednode *)headnode{ return _headnode;}- (bbsinglelinkednode *)lastnode{ bbsinglelinkednode *last = _headnode; while (last.next) { last = last.next; } return last;}- (void)reverse{ bbsinglelinkednode *prev = nil; bbsinglelinkednode *current = _headnode; bbsinglelinkednode *next = nil; while (current) { next = current.next; current.next = prev; prev = current; current = next; } _headnode = prev;}- (void)readallnode{ bbsinglelinkednode *tmpnode = _headnode; while (tmpnode) { nslog(@"node key -- %@, node value -- %@", tmpnode.key, tmpnode.value); tmpnode = tmpnode.next; }}- (nsinteger)length{ nsinteger _len = 0; for (bbsinglelinkednode *node = _headnode; node; node = node.next) { _len ++; } return _len;}- (bool)isempty{ return _headnode == nil;}#pragma mark - private- (bbsinglelinkednode *)nodebeforenode:(bbsinglelinkednode *)node{ bbsinglelinkednode *targetnode = nil; bbsinglelinkednode *tmpnode = _headnode; while (tmpnode) { if ([tmpnode.next isequal:node]) { targetnode = tmpnode; break; } else { tmpnode = tmpnode.next; } } return targetnode;}- (bool)isnodeexists:(bbsinglelinkednode *)node{ bbsinglelinkednode *tmpnode = _headnode; while (tmpnode) { if ([tmpnode isequal:node]) { return yes; } tmpnode = tmpnode.next; } return false;}@end |
双链表
双链表提供了插入、删除、查询操作，具体实现如下：
bblinkedmap.h
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#import <foundation/foundation.h>@interface bblinkednode : nsobject <nscopying>@property (nonatomic, strong) nsstring *key;@property (nonatomic, strong) nsstring *value;@property (nonatomic, strong) bblinkednode *prev;@property (nonatomic, strong) bblinkednode *next;- (instancetype)initwithkey:(nsstring *)key value:(nsstring *)value;+ (instancetype)nodewithkey:(nsstring *)key value:(nsstring *)value;@end@interface bblinkedmap : nsobject- (void)insertnodeathead:(bblinkednode *)node;- (void)insertnode:(bblinkednode *)node;- (void)insertnode:(bblinkednode *)newnode beforenodeforkey:(nsstring *)key;- (void)insertnode:(bblinkednode *)newnode afternodeforkey:(nsstring *)key;- (void)bringnodetohead:(bblinkednode *)node;- (void)readallnode;- (void)removenodeforkey:(nsstring *)key;- (void)removetailnode;- (nsinteger)length;- (bool)isempty;- (bblinkednode *)nodeforkey:(nsstring *)key;- (bblinkednode *)headnode;- (bblinkednode *)tailnode;@end |
bblinkedmap.m
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#import "bblinkedmap.h"@implementation bblinkednode- (instancetype)initwithkey:(nsstring *)key value:(nsstring *)value{ if (self = [super init]) { _key = key; _value = value; } return self;}+ (instancetype)nodewithkey:(nsstring *)key value:(nsstring *)value{ return [[[self class] alloc] initwithkey:key value:value];}#pragma mark - nscopying- (id)copywithzone:(nullable nszone *)zone{ bblinkednode *newnode = [[bblinkednode allocwithzone:zone] init]; newnode.key = self.key; newnode.value = self.value; newnode.prev = self.prev; newnode.next = self.next; return newnode;}@end@interface bblinkedmap ()@property (nonatomic, strong) bblinkednode *headnode;@property (nonatomic, strong) bblinkednode *tailnode;@property (nonatomic, strong) nsmutabledictionary *innermap;@end@implementation bblinkedmap- (instancetype)init{ self = [super init]; if (self) { _innermap = [nsmutabledictionary new]; } return self;}#pragma mark - public- (void)insertnodeathead:(bblinkednode *)node{ if (!node || node.key.length == 0) { return; } if ([self isnodeexists:node]) { return; } _innermap[node.key] = node; if (_headnode) { node.next = _headnode; _headnode.prev = node; _headnode = node; } else { _headnode = _tailnode = node; }}- (void)insertnode:(bblinkednode *)node{ if (!node || node.key.length == 0) { return; } if ([self isnodeexists:node]) { return; } if (!_headnode && !_tailnode) { _headnode = _tailnode = node; return; } _innermap[node.key] = node; _tailnode.next = node; node.prev = _tailnode; _tailnode = node;}- (void)insertnode:(bblinkednode *)newnode beforenodeforkey:(nsstring *)key{ if (key.length == 0 || !newnode || newnode.key.length == 0) { return; } if ([self isnodeexists:newnode]) { return; } if (!_headnode && !_tailnode) { _headnode = _tailnode = newnode; return; } bblinkednode *node = _innermap[key]; if (node) { _innermap[newnode.key] = newnode; if (node.prev) { node.prev.next = newnode; newnode.prev = node.prev; } else { _headnode = newnode; } node.prev = newnode; newnode.next = node; } else { [self insertnode:newnode]; //insert to tail } }- (void)insertnode:(bblinkednode *)newnode afternodeforkey:(nsstring *)key{ if (key.length == 0 || !newnode || newnode.key.length == 0) { return; } if ([self isnodeexists:newnode]) { return; } if (!_headnode && !_tailnode) { _headnode = _tailnode = newnode; return; } bblinkednode *node = _innermap[key]; if (node) { _innermap[newnode.key] = newnode; if (node.next) { newnode.next = node.next; node.next.prev = newnode; } else { _tailnode = newnode; } newnode.prev = node; node.next = newnode; } else { [self insertnode:newnode]; //insert to tail }}- (void)bringnodetohead:(bblinkednode *)node{ if (!node) { return; } if (!_headnode && !_tailnode) { _headnode = _tailnode = node; return; } if ([_headnode isequal:node]) { return; } if ([_tailnode isequal:node]) { _tailnode = node.prev; _tailnode.next = nil; } else { node.prev.next = node.next; node.next.prev = node.prev; } _headnode.prev = node; node.next = _headnode; node.prev = nil; _headnode = node;}- (void)removenodeforkey:(nsstring *)key{ if (key.length == 0) { return; } bblinkednode *node = _innermap[key]; if (!node) { return; } [_innermap removeobjectforkey:key]; if ([_headnode isequal:node]) { _headnode = node.next; } else if ([_tailnode isequal:node]) { _tailnode = node.prev; } node.prev.next = node.next; node.next.prev = node.prev; }- (void)removetailnode{ if (!_tailnode || _tailnode.key.length == 0) { return; } [_innermap removeobjectforkey:_tailnode.key]; if (_headnode == _tailnode) { _headnode = _tailnode = nil; return; } _tailnode = _tailnode.prev; _tailnode.next = nil;}- (bblinkednode *)nodeforkey:(nsstring *)key{ if (key.length == 0) { return nil; } bblinkednode *node = _innermap[key]; return node;}- (bblinkednode *)headnode{ return _headnode;}- (bblinkednode *)tailnode{ return _tailnode;}- (void)readallnode{ bblinkednode *node = _headnode; while (node) { nslog(@"node key -- %@, node value -- %@", node.key, node.value); node = node.next; }}- (nsinteger)length{ nsinteger _len = 0; for (bblinkednode *node = _headnode; node; node = node.next) { _len ++; } return _len;}- (bool)isempty{ return _headnode == nil;}#pragma mark - private- (bool)isnodeexists:(bblinkednode *)node{ bblinkednode *tmpnode = _headnode; while (tmpnode) { if ([tmpnode isequal:node]) { return yes; } tmpnode = tmpnode.next; } return false;}@end |
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原文链接：http://www.jianshu.com/p/12fe060811f2?utm_source=tuicool&utm_medium=referral
