How to do a simple random sort of values within an array

Question

I need to sort these values randomly in an array.

int [] d = new int[26];  
        d[0]=1;  
        d[1]=5;  
        d[2]=10;  
        d[3]=25;  
        d[4]=50;    
        d[5]=75;  
        d[6]=100;  
        d[7]=200;  
        d[8]=300;  
        d[9]=400;  
        d[10]=500;  
        d[11]=750;  
        d[12]=1000;  
        d[13]=2000;  
        d[14]=3000;  
        d[15]=4000;  
        d[16]=5000;  
        d[17]=7500;  
        d[18]=10000;  
        d[19]=25000;   
        d[20]=50000;  
        d[21]=100000;  
        d[22]=250000;  
        d[23]=500000;  
        d[24]=750000;  
        d[25]=1000000;

Possible duplicate : http://stackoverflow.com/questions/375351/most-efficient-way-to-randomly-sort-shuffle-a-list-of-integers-in-c — rlb.usa, Apr 29 '11 at 18:59
btw. `sort` and `random` are, essentially contradictory terms, unless you're talking about something like Bogosort. — aviraldg, Apr 29 '11 at 18:59

score 0 · Answer 1 · answered Feb 25 '13 at 16:57

0

If it's java you may use

Arrays.shuffle(d);

answered Feb 25 '13 at 16:57

RiaD

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score 0 · Answer 2 · answered Apr 29 '11 at 19:01

0

Assuming you are writing this in C++ you can use random_shuffle function template from the Standard library. http://www.cppreference.com/wiki/algorithm/random_shuffle

answered Apr 29 '11 at 19:01

score 0 · Answer 3 · edited May 23 '17 at 11:47

If you want to write your own function, simply take two random indices and swap their values. Put that in a loop and do it as many times as think necessary for the array to be well shuffled (I would say a number of times equal to two times the number of elements in the array).

In psudo-code (since you haven't indicated the language)

NUMBER_OF_SHUFFLES = 2;    
for(ix = 0; ix < NUMBER_OF_SHUFFLES * myArray.length; ix++)
    index1 = random(myArray.length)
    index2 = random(myArray.length)
    temp = index1

    myArray[index1] = myArray[index2]
    myArray[index2] = temp

There are more sophisticated ways of doing it as well. Check out this discussion: An Efficient way of randomizing an array - Shuffle code

How to do a simple random sort of values within an array

3 Answers3