a與b比較浆竭，比較的結(jié)果返回為-1浸须，0，1邦泄。
為1:a<b
為0:a==b
為1:a>b
二叉樹中小于當(dāng)前變量在左邊删窒，大于在右邊。
Java中TreeSet運(yùn)用了二叉樹的原理顺囊，可以對(duì)時(shí)間進(jìn)行排序肌索。為了方便查看，所以將日期作為一個(gè)類特碳，將年月日聲明為屬性诚亚。
//Data類
int day;
int month;
int year;
public MyDate(int day,int month,int year)
{
this.day= day;
this.month= month;
this.year= year;
}
//實(shí)現(xiàn)類
Set set =newTreeSet();
set.add(new Date(2,11,1982);
set.add(new Date(3,11,1989);
set.add(new Date(10,11,1990);
打印的結(jié)果： 3/11/1981
2/11/1982
10/11/1990
OC中的實(shí)現(xiàn)日期的排序
NSComparisonResult res = [obj1 compare: obj2];
res = NSOrderedAscending obj1 < obj2;
res = NSOrderedSame obj1 == obj2;
res = NSOrderedDescending obj1 > obj2;
OC中有compare方法晕换，這個(gè)方法是對(duì)兩個(gè)對(duì)象進(jìn)行比較，比較的結(jié)果是-1,0,1,也就是說(shuō)兩個(gè)對(duì)象的大小比較亡电。
那么和在上述java中的代碼一樣届巩，數(shù)組的中進(jìn)行排序。
//Date類.m文件中
-(instancetype)initWithYear:(int)year Month:(int)month Day:(int)day
{
self = [super init];
if (self) {
self.year = year;
self.month = month;
self.day = day;
}
return self;
}
//重寫compare方法
- (NSComparisonResult)compare:(id)other
{
Date *d = (Date*)other;
//日期完全相等
if (self.year == d.year && self.month == d.month && self.day == d.day) {
return NSOrderedSame;
}
//date1年 > date2
if (self.year > d.year) {
return NSOrderedDescending;
//年相同
}else if(self.year == d.year){
//月不同
if (self.month > d.month) {
return NSOrderedDescending;
//月相同
}else if(self.month == d.month){
//日不同
if (self.day > d.day) {
return NSOrderedDescending;
}else{
return NSOrderedAscending;
}
}else{
return NSOrderedAscending;
}
}
return NSOrderedAscending;
}
下面是測(cè)試結(jié)果
Date *date = [[Date alloc]initWithYear:2000 Month:10 Day:11];
Date *date1 = [[Date alloc]initWithYear:2000 Month:11 Day:11];
Date *date2 = [[Date alloc]initWithYear:2000 Month:10 Day:10];
Date *date3 = [[Date alloc]initWithYear:1999 Month:10 Day:11];
Date *date4 = [[Date alloc]initWithYear:2001 Month:10 Day:11];
NSMutableArray *arr = [NSMutableArray arrayWithObjects:date,date1,date2,date3,date4, nil];
for (int i=0; i<arr.count; i++) {
for (int j = i+1; j<arr.count-1; j++) {
//冒泡排序
Date *d = arr[i];
Date *d1 = arr[j];
if ([d compare:d1]) {
Date *temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
for (int i = 0; i<arr.count; i++) {
Date *date = arr[i];
NSLog(@"%d-%d-%d",date.year,date.month,date.day);
}
2017-03-08 23:31:39.418 DateSet[35781:606761] 1999-10-11
2017-03-08 23:31:39.418 DateSet[35781:606761] 2000-10-10
2017-03-08 23:31:39.418 DateSet[35781:606761] 2000-11-11
2017-03-08 23:31:39.418 DateSet[35781:606761] 2000-10-11
2017-03-08 23:31:39.418 DateSet[35781:606761] 2001-10-11
