Comments on: The Shuffle http://www.technicalinterviews.net/the-shuffle/ This site features a collection of common technical interview questions gathered by a group of programmers who have been through, and given, lots of technical interviews. There is an emphasis on C++ and game programming technical interviews, but most of the questions are relevant to any technical interview. Thu, 04 Dec 2008 19:15:33 +0000 http://wordpress.org/?v=2.0.7 by: Sundar http://www.technicalinterviews.net/the-shuffle/#comment-1254 Thu, 12 Jul 2007 12:52:26 +0000 http://www.technicalinterviews.net/the-shuffle/#comment-1254 Let X1, X2…. XN (In this case N=52) be the set of N numbers to be shuffled. 1. Set j to N 2. Generate a random number R. (uniformly distributed between 0 and 1) 3. Set k to (jR+1). k is now a random integer, between 1 and j. 4. Exchange Xk and Xj 5. Decrease j by 1. 6. If j > 1, return to step 2. void KnuthShuffle(int* pArr) { int rand; for(int i=51;i>=0;i--) { rand=GenRand(0,i); swap(pArr[i], pArr[rand]); } } GenRand(int min, int max) generates a random number between min and max. Let X1, X2…. XN (In this case N=52) be the set of N numbers to be shuffled.

1. Set j to N
2. Generate a random number R. (uniformly distributed between 0 and 1)
3. Set k to (jR+1). k is now a random integer, between 1 and j.
4. Exchange Xk and Xj
5. Decrease j by 1.
6. If j > 1, return to step 2.

void KnuthShuffle(int* pArr)
{
int rand;
for(int i=51;i>=0;i–)
{
rand=GenRand(0,i);
swap(pArr[i], pArr[rand]);
}
}

GenRand(int min, int max) generates a random number between min and max.

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