java - Generating unique random numbers and check duplicates -

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• how generate random integers within specific range in java? 49 answers

i generate 3*6 digits, can form array of 3rows*6cols. don't want duplicated found in column. can anywhere, in same row, in each column, there shouldn't duplicate of same number. there algorithm generating ?

fill matrix column-wise , use set keep track of numbers have used in current column. can use do-while statement each cell, in pseudo-code:

for each column {   used = new set   each cell in column {     {       num = generate random number     } while (num in used)     add num used     add num current cell   } }