How to sort an Array of signed numbers in iOS?

问题

This may be a simple question, but i don't know the way of doing sorting of array of signed integer values.

My array before sorting,

pointsAry (-2,-7,-5,0,-3,2,-1,-4,1,3,-6)

After using

NSArray * sortedArray = [pointsAry sortedArrayUsingComparator:^(id str1, id str2){
        return [(NSString *)str1 compare:(NSString *)str2 options:NSNumericSearch];
    }];

Result

sortedArray : (-1,-2,-3,-4,-5,-6,-7,0,1,2,3)

for signed values the sortedArray format is not correct, so i need like

(-7,-6,-5,-4,-3,-2,-1,0,1,2,3)

How to sort like above format ? Thanks in advance.

回答1:

NSArray *sortedArray = [pointsAry sortedArrayUsingComparator:^(NSString *str1, NSString *str2){
    return [@([str1 intValue]) compare:@([str2 intValue])];
}];

回答2:

The following comparator avoids the creation of temporary NSNumber objects:

NSArray *sortedArray = [pointsAry sortedArrayUsingComparator:^NSComparisonResult(NSString *str1, NSString *str2) {
    return my_int_compare([str1 intValue], [str2 intValue]);
}];

where

static inline int my_int_compare(int x, int y) { return (x > y) - (x < y); }

is a helper function that compares two integers and returns -1, 0, or +1 (as required for a comparator method), using the technique from

Is there a standard sign function (signum, sgn) in C/C++?.

Of course the problem only arises because the array contains NSString objects. Using NSNumbers would be the better solution.

Using the NSNumericSearch option does not help because it does not treat the minus sign as part of the number.

回答3:

NSMutableArray *array = [[NSMutableArray alloc] initWithObjects:@"P3",@"P1",@"P4",@"P10", nil];
    NSMutableArray *num=[[NSMutableArray alloc]init];
    for(int i=0;i<array.count;i++)
    {
        NSString *str=array[i];
       [num addObject: [str substringFromIndex:1]];
    }



    NSArray *sortedArray = [num sortedArrayUsingComparator:^(NSString *str1, NSString *str2){
        return [@([str1 intValue]) compare:@([str2 intValue])];
    }];
    [array removeAllObjects];
    for(int i=0;i<sortedArray.count;i++)
    {
        NSString *newString = [NSString stringWithFormat:@"P%@",sortedArray[i]];


        [array addObject:newString];
    }

It's work for me

来源：https://stackoverflow.com/questions/20212998/how-to-sort-an-array-of-signed-numbers-in-ios

标签

ios

iphone

objective-c

sorting

nsarray