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last digit ending with 7

Posted on 2014-10-10
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Last Modified: 2014-10-11
Hi,
I am trying below challenge

http://codingbat.com/prob/p125339

I wrote as below

public boolean lastDigit(int a, int b) {
if(a%10==7 && b%7==7){
return true;
}
return false;

 
}


I have test cases failing as below
Expected      Run            
lastDigit(7, 17) → true      false      X         
lastDigit(6, 17) → false      false      OK         
lastDigit(3, 113) → true      false      X         
lastDigit(114, 113) → false      false      OK         
lastDigit(114, 4) → true      false      X         
lastDigit(10, 0) → true      false      X         
lastDigit(11, 0) → false      false      OK         


How to improve and fix my program
0
Comment
Question by:gudii9
9 Comments
 
LVL 7

Author Comment

by:gudii9
ID: 40373137
public boolean lastDigit(int a, int b) {
if(a%10==7&& b%10==7){
return true;
}

if(a%10==7&& b%10==7){
return true;
}

if(a%10==1&& b%10==1){
return true;
}

if(a%10==2&& b%10==2){
return true;
}

if(a%10==3&& b%10==3){
return true;
}

if(a%10==7&& b%10==7){
return true;
}

if(a%10==4&& b%10==4){
return true;
}

if(a%10==5&& b%10==5){
return true;
}

if(a%10==6&& b%10==6){
return true;
}

if(a%10==8&& b%10==8){
return true;
}

if(a%10==9&& b%10==9){
return true;
}

if(a%10==0&& b%10==0){
return true;
}
return false;

  
}

Open in new window



Expected      Run            
lastDigit(7, 17) → true      true      OK         
lastDigit(6, 17) → false      false      OK         
lastDigit(3, 113) → true      true      OK         
lastDigit(114, 113) → false      false      OK         
lastDigit(114, 4) → true      true      OK         
lastDigit(10, 0) → true      true      OK         
lastDigit(11, 0) → false      false      OK         

Actually i modifed the code but still looks lengthy code. Please advise how to simplify and improve my code above
0
 
LVL 28

Expert Comment

by:rrz
ID: 40373181
What is wrong with the solution given when you click on the "Show Solution" button(at posted link)?
0
 
LVL 85

Accepted Solution

by:
ozo earned 1400 total points
ID: 40373188
return a%10 == b%10;
0
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LVL 7

Author Comment

by:gudii9
ID: 40373198
I would like to work the solution myself and improve and correct my own mistakes. I am not looking at the solutions at this point as they seems too complex for me at times.
0
 
LVL 85

Expert Comment

by:ozo
ID: 40373213
return (a-b)%10 == 0;
0
 
LVL 7

Author Comment

by:gudii9
ID: 40373565
How both below statements are same? Please advise

return(a % 10 == b % 10);
 

return (a-b)%10 == 0;
0
 
LVL 28

Assisted Solution

by:dpearson
dpearson earned 600 total points
ID: 40374075
a % 10 returns the remainder when you divide by 10.  So "15 % 10" is 5.

So (a % 10 == b % 10) is true when both a and b have the same remainder when divided by 10.  E.g 25 and 15.

(a - b) % 10 returns the remainder when you divide the difference between the two values by 10.

So if we go back to our example (25 and 15) then the difference is 10 and if we figure out the remainder when we divide that by 10, we'll get 0.

So they're just 2 equivalent ways of saying the same thing.
For my money "a % 10 == b % 10" is the clearer of the two.

Doug
0
 
LVL 7

Author Comment

by:gudii9
ID: 40375100
So if we go back to our example (25 and 15)

Open in new window


instead if i pass (15 and 25) difference is -10(not positive number)
still the reminder does not effect right? it is still 0.

Please advise
0
 
LVL 85

Expert Comment

by:ozo
ID: 40375135
There are differences in how various languages handle % for negative integers, but all of them should agree when the answer is 0
0

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