In the app that I am making, I am using a segmented button to control adding or subtracting a number by one or two, the only problem is that I dont know how to add/subrtact a number by two based on the method that I use to add or subtract by one. This is the code that I have in my app to add or subtract by one:
int number = 0;
-(IBAction)IncrementNumber:(id)sender {
number++;
[currentNumber setText:[NSString stringWithFormat:#"%d", number]];
}
-(IBAction)DecrementNumber:(id)sender {
number--;
[currentNumber setText:[NSString stringWithFormat:#"%d", number]];
}
Based on this code, how would I go twards adding or subtracting by two or even three?
Or more verbal:
number = number + n;
number = number - n;
(Where n is the number you want to add/substract.)
number += 2;
number -= 2;
Generalization:
number += n;
number -= n;
If you have somewhere else where you are setting the amount for incrementing or decrementing something use that number as n.
Related
I want to count how many number of zero(0) before numeric number. Because I need to save those number which is present before numeric.
Exam:- suppose I have a number 0000102. So I want to calculate how many zero(0) before numeric start. In this exam we are see here is 4 zero's(0) are present. It is possible to calculate this?
for (i=0;i<string.length;i++)
{
if ([[string characterAtIndex:i] intValue] <= 9 || [[string characterAtIndex:i] intValue] > 0 )
{
i++;
}
else
{
numerOfZeros++;
}
}
int count = 0;
NSString *strr = #"0000102";
unichar findC;
for (int i = 0; i<strr.length; i++)
{
findC = [strr characterAtIndex:i];
if (findC == '0')
{
count++;
}
else
break;
}
NSLog(#"%d",count);
Recursive approach for a one liner:
#implementation NSString (category)
- (NSUInteger)zeroPrefixCount
{
return [string hasPrefix:#"0"] ? 1 + [[string substringFromIndex:1] zeroPrefixCount] : 0;
}
#end
This is not an optimal solution, performance-wise, but it's typical of your first days at programming classes.
usage
// x will be 4
NSUInteger x = [#"0000102" zeroPrefixCount];
I recommend you to save this kind of numbers as String itself and no need to further evaluate how many zeros are there rather do a string comparison if needed.
If you really want to count zeros in your number then you can consider converting it to a string and use NSRange and NSString helper methods to get what you want. Similar situation is answered here.
search if NSString contains value
First of all I must admit that it is my assignment. But I am not asking anyone to solve it but I am working hard to solve it and need help with my algorithm.
I have an array of weights that is assigned to leftSide and rightSide of a scale. I need to balance the weights in right side and left side using the weights in the array.
I have the following code but it does not cover all the situations:
-(BOOL) isBalanced
{
_weights = [NSMutableArray arrayWithArray:#[#3,#4,#2,#1,#5,#6,#4]];
self.leftSide = [[_weights objectAtIndex:arc4random() % 7] integerValue]; // random weight
self.rightSide = [[_weights objectAtIndex:arc4random() % 7] integerValue]; // random weight
if(self.leftSide == self.rightSide) return YES; // already balanced
if(self.leftSide > self.rightSide)
{
// add weights on right side
int difference = self.leftSide - self.rightSide;
int index = [_weights indexOfObject:[NSNumber numberWithInt:difference]];
self.rightSide += [[_weights objectAtIndex:index] integerValue];
NSLog(#"%d",index);
}
else
{
int difference = self.rightSide - self.leftSide;
int index = [_weights indexOfObject:[NSNumber numberWithInt:difference]];
self.leftSide += [[_weights objectAtIndex:index] integerValue];
NSLog(#"%d",index);
}
return self.leftSide == self.rightSide;
}
UPDATE:
To simplify! I have a number 6 and now I need to search inside an array of ints if any of the numbers can be added together to get 6. Example:
1,2,3,5,4
In the above array I can take 1+2+3 which makes 6. I can also take 4+2 which is 6. The question is how do I find those individual numbers that can sum up to the number 6.
This question already has answers here:
iOS: How do I generate 8 unique random integers?
(6 answers)
Closed 9 years ago.
I have 10 UIButtons created in historyboard, OK?
I want to add random numbers that do not repeat these numbers, ie, numbers from 0 to 9 that interspersed whenever the View is loaded.
I tried to find on Google and here a way to use my existing buttons ( 10 UIButton ), and just apply them to random values. Most ways found ( arc4random() % 10 ), repeat the numbers.
Here's one
here's another
here's another
All results found that creating buttons dynamically. Anyone been through this?
Create an array of the numbers. Then perform a set of random swapping of elements in the array. You now have your unique numbers in random order.
- (NSArray *)generateRandomNumbers:(NSUInteger)count {
NSMutableArray *res = [NSMutableArray arrayWithCapacity:count];
// Populate with the numbers 1 .. count (never use a tag of 0)
for (NSUInteger i = 1; i <= count; i++) {
[res addObject:#(i)];
}
// Shuffle the values - the greater the number of shuffles, the more randomized
for (NSUInteger i = 0; i < count * 20; i++) {
NSUInteger x = arc4random_uniform(count);
NSUInteger y = arc4random_uniform(count);
[res exchangeObjectAtIndex:x withObjectAtIndex:y];
}
return res;
}
// Apply the tags to the buttons. This assumes you have 10 separate ivars for the 10 buttons
NSArray *randomNumbers = [self generateRandomNumbers:10];
button1.tag = [randomNumbers[0] integerValue];
button2.tag = [randomNumbers[1] integerValue];
...
button10.tag = [randomNumbers[9] integerValue];
#meth has the right idea. If you wanna make sure the numbers aren't repeating, try something like this: (note: top would the highest number to generate. Make sure this => amount or else this will loop forever and ever and ever ;)
- (NSArray*) makeNumbers: (NSInteger) amount withTopBound: (int) top
{
NSMutableArray* temp = [[NSMutableArray alloc] initWithCapacity: amount];
for (int i = 0; i < amount; i++)
{
// make random number
NSNumber* randomNum;
// flag to check duplicates
BOOL duplicate;
// check if randomNum is already in your array
do
{
duplicate = NO;
randomNum = [NSNumber numberWithInt: arc4random() % top];
for (NSNumber* currentNum in temp)
{
if ([randomNum isEqualToNumber: currentNum])
{
// now we'll try to make a new number on the next pass
duplicate = YES;
}
}
} while (duplicate)
[temp addObject: randomNum];
}
return temp;
}
I want to write a really simple prime app. But i am having some problems with the code below it should generate primes from 0 to 99. But instead it just shows 99.
One problem is that only the last number is displayed. But the other one is that the prime "check" doesn't work. How can I fix those problems.
for (i=0; i<100; i++) {
for (n=2; n<i; n++) {
if (i%n == 0) break;
else primetext.text = [NSString stringWithFormat:#"%i, ", i];
}
}
There were a number of problems, I'll try to explain them
The problem with prime checking was that you had the if-else statement inside of the for loop that iterated through the numbers to check. So if your number wasn't divisible by ANY of the numbers you check it would be registered as prime. It would also be registered n times, where n is the number of times it was found to not be divisible.
All even numbers are not prime (aside from 2), so you can do i+=2 to double your speed
You only need to check up to the square root of a number to see if it's prime.
1 isn't a prime so you don't need to include it (especially because it can make your logic more complex).
You were reassigning the string instead of adding a component to it
You were using %i instead of %d. This can sometimes cause weird errors.
Here is your method revised with these points in mind.
int maxNum = 100;
primetext.text = #"2 "; //Start knowing that 2 is the lowest prime (avoid evaluating evens)
for (i=3; i<=maxNum; i+=2) //Start at 3 and add 2 (avoid 1 and 2 as well as even numbers)
{
bool isPrime = YES; //Assume that i is prime
for (n=2; n<sqrt(i); n++) //Divide by every number up to square root
{
if (i%n == 0) //If evenly divisible by n, not a prime
{
isPrime = NO;
break; //Don't need to check any more factors, so break
}
}
if (isPrime) //If isPrime was never set to NO, i is prime
{
NSString *temp = [NSString stringWithFormat:#"%d ", i];
primetext.text = [primetext.text stringByAppendingString:temp];
}
}
Hope this helps.
You should append the number to primetext.text instead of assigning. Right now it's being reassigned on every iteration.
I'm trying to divide an array into individual arrays of four elements, where the last array will contain the reminder. For example, if that main array's length property will be ten, three subarrays will be created - two consisting of four elements, and one of two elements.
The code I have right now looks like the following:
NSMutableArray *mainMutableArray = [NSMutableArray arrayWithObjects:#"First", #"Second", #"Third", #"Fourth", #"Fifth", #"Sixth", #"Seventh", #"Eighth", nil];
NSMutableArray *mutableArrayOfSubarrays = [NSMutableArray array];
int length = mainMutableArray.count / 4;
int location = 0;
for (int i = 0; i < length; i++)
{
[mutableArrayOfSubarrays addObject:[mainMutableArray subarrayWithRange:NSMakeRange(location, 4)]];
location += 4;
}
This of course works only when the reminder is equal to 0.
Any help would be greatly appreciated.
Ok, here we go:
int length = mainMutableArray.count;
for (int location = 0; location < length; location+=4)
{
unsigned int Size=length-location;
if (Size>4) Size=4;
[mutableArrayOfSubarrays addObject:[mainMutableArray subarrayWithRange:NSMakeRange(location, Size)]];
}
If you use a while loop, you can make the condition describe what you are actually trying to do:
NSUInteger length = [mainMutableArray count];
NSUInteger location = 0;
// Until the location is less than four away from the end
while( location <= (length - 4) ){
[mutableArrayOfSubarrays addObject:[mainMutableArray subarrayWithRange:NSMakeRange(location, 4)]];
location += 4;
}
// Pick up the remainder, if any
if( location != length ){
[mutableArrayOfSubarrays addObject:[mainMutableArray subarrayWithRange:NSMakeRange(location, length-location)]];
}
Loop from length*4 to mainMutableArray.count to get the remainder of the array.