Rounding to specific value? - ios

Question

I need to round a number, let's say 543 to either the hundreds or the tens place. It could be either one, as it's part of a game and this stage can ask you to do one or the other.
So for example, it could ask, "Round number to nearest tens", and if the number was 543, they would have to enter in 540.
However, I don't see a function that you can specify target place value to round at. I know there's an easy solution, I just can't think of one right now.
From what I see, the round function rounds the last decimal place?
Thanks

Answer 1

To rounding to 100's place
NSInteger num=543;
NSInteger deci=num%100;//43
if(deci>49){
num=num-deci+100;//543-43+100 =600
}
else{
num=num-deci;//543-43=500
}
To round to 10's place
NSInteger num=543;
NSInteger deci=num%10;//3
if(deci>4){
num=num-deci+100;//543-3+10 =550
}
else{
num=num-deci;//543-3=540
}
EDIT:
Tried to merge the above in one:
NSInteger num=543;
NSInteger place=100; //rounding factor, 10 or 100 or even more.
NSInteger condition=place/2;
NSInteger deci=num%place;//43
if(deci>=condition){
num=num-deci+place;//543-43+100 =600.
}
else{
num=num-deci;//543-43=500
}

Answer 2

You may just use an algorithm in your code:
For example, lets say that you need to round up a number to hundred's place.
int c = 543
int k = c % 100
if k > 50
c = (c - k) + 100
else
c = c - k

Answer 3

To round numbers, you can use the modulus operator, %.
The modulus operator gives you the remainder after division.
So 543 % 10 = 3, and 543 % 100 = 43.
Example:
int place = 10;
int numToRound=543;
// Remainder is 3
int remainder = numToRound%place;
if(remainder>(place/2)) {
// Called if remainder is greater than 5. In this case, it is 3, so this line won't be called.
// Subtract the remainder, and round up by 10.
numToRound=(numToRound-remainder)+place;
}
else {
// Called if remainder is less than 5. In this case, 3 < 5, so it will be called.
// Subtract the remainder, leaving 540
numToRound=(numToRound-remainder);
}
// numToRound will output as 540
NSLog(#"%i", numToRound);
Edit: My original answer was submitted before it was ready, because I accidentally hit a key to submit it. Oops.