Lintcode:first Bad Version Problem solving report

First Bad Version

Http://lintcode.com/en/problem/first-bad-version

The code base version is a integer and start from 1 to N. One day, someone commits a bad version of the code case, so it caused itself and the following versions is all failed in t He unit tests.

You can determine whether a version was bad by the following interface:

 

 java: 
     public VersionControl {
     } 
 c++: 
     class VersionControl {
     public: 
         bool isbadversion (int version); 
     }; 
 python: 
     class VersionControl: 
 

Find the first bad version.

Note

You should call Isbadversion as few as possible.

Please read the annotation in code area to get the correct-on-the-isbadversion in different language. For example, Java is versioncontrol.isbadversion.

Example

Given n=5

Call Isbadversion (3), Get false

Call Isbadversion (5), Get True

Call Isbadversion (4), Get True

Return 4 is the first bad version

Challenge

Don't call isbadversion exceed O (Logn) times.

Tags ExpandSolution 1:Nine Chapters algorithm template solution, note, must use Left + 1 < Right as the condition of while, this will not produce a dead loop and cross-border situation.

1 /**2 * public class VersionControl {3 * public static Boolean isbadversion (int k);4  * }5 * can use Versioncontrol.isbadversion (k) to judge wether6 * The KTH code version is bad or not.7 */8 classSolution {9     /**Ten      * @paramn:an integers. One      * @return: An integer which are the first bad version. A      */ -      Public intFindfirstbadversion (intN) { -         //Write your code here the         if(n = = 1) { -             return1; -         } -          +         intleft = 1; -         intright =N; +          A          while(Left + 1 <Right ) { at             intMid = left + (right-left)/2; -             if(Versioncontrol.isbadversion (mid)) { -right =mid; -}Else { -left =mid; -             } in         } -          to         if(Versioncontrol.isbadversion (left)) { +             returnLeft ; -         } the          *         returnRight ; $     }Panax Notoginseng}

View CodeSolution 2:

You can also simplify a little bit:

1 /**2 * public class VersionControl {3 * public static Boolean isbadversion (int k);4  * }5 * can use Versioncontrol.isbadversion (k) to judge wether6 * The KTH code version is bad or not.7 */8 classSolution {9     /**Ten      * @paramn:an integers. One      * @return: An integer which are the first bad version. A      */ -      Public intFindfirstbadversion (intN) { -         //Write your code here the         if(n = = 1) { -             return1; -         } -          +         intleft = 1; -         intright =N; +          A          while(Left <Right ) { at             intMid = left + (right-left)/2; -             if(Versioncontrol.isbadversion (mid)) { -right =mid; -}Else { -left = mid + 1; -             } in         } -          to         returnRight ; +     } -}

View Code

Lintcode:first Bad Version Problem solving report