NSSet
去掉数组中重复的数
NSSet方法
NSArray *arr = @[@11,@33,@44,@42,@22,@11,@44,@11];
NSSet *set = [NSSet setWithArray:arr];
//集合判断一个数组里面是否包含一个对象，速度最快，若重复很多次，应该考虑用集合
//NSOrderedSet
[set containsObject:@11];
arr = [set allObjects];
NSDictionary方法
NSArray *arr = @[@11,@33,@44,@42,@22,@11,@44,@11];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[arr enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
dict[obj] = @1;
}];
arr = [dict allKeys];
NSLog(@"%@",arr);
数组排序
NSArray *arr2 = @[@11,@33,@44,@42,@22,@11,@44,@11];
NSMutableArray *arr1 = arr2.mutableCopy;
for (int i = 0; i < arr1.count; i++) {
for (int j = 0; j < arr1.count; j++) {
if (arr1[i] > arr1[j]) {
[arr1 exchangeObjectAtIndex:i withObjectAtIndex:j];
}
}
}
冒泡排序
//冒泡排序
for (int i = 0; i < arr1.count; i++) {
for (int j = 0; j < arr1.count - 1 - i; j++) {
if (arr1[j] > arr1[j + 1]) {
[arr1 exchangeObjectAtIndex:j withObjectAtIndex:j + 1];
}
}
}
sort方法排序(快排)
[arr1 sortUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
if (obj1 > obj2) {
//降
return NSOrderedDescending;
}else if(obj1 < obj2){
//升
return NSOrderedAscending;
}
else {
return NSOrderedSame;
}
}];
