Generate random numbers without repeating a value: Difference between revisions
Generate random numbers without repeating a value (view source)
Revision as of 17:11, 12 May 2022
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(→{{header|Haskell}}: Consolidated two very similar versions) |
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Line 866:
<pre>
[4, 19, 13, 8, 14, 6, 18, 20, 11, 16, 17, 7, 5, 9, 2, 15, 3, 1, 10, 12]
</pre>
=={{header|Vlang}}==
{{trans|go}}
<lang vlang>import rand
import rand.seed
fn generate(from i64, to i64) {
if to < from || from < 0 {
println("Invalid range.")
}
span := int(to - from + 1)
mut generated := []bool{len: span} // all false by default, zero indexing
mut count := span
for count > 0 {
n := from + rand.i64n(span) or {0} // upper endpoint is exclusive
if !generated[n-from] {
generated[n-from] = true
print("${n} ")
count--
}
}
println('')
}
fn main(){
rand.seed(seed.time_seed_array(2))
// generate 5 sets say
for i := 1; i <= 5; i++ {
generate(1, 20)
}
}</lang>
{{out}}
<pre>Same as Go entry</pre>
Alternatively and far more efficiently, we can simply create a list of the required numbers and randomly shuffle them. Vlang has a standard library function for this which uses the Fisher-Yates (aka Knuth) shuffle.
<lang vlang>import rand
import rand.seed
fn main(){
rand.seed(seed.time_seed_array(2))
mut numbers := []int{len:20, init:it+1}
// generate 5 sets say
for i := 1; i <= 5; i++ {
rand.shuffle<int>(mut numbers, rand.ShuffleConfigStruct{})?
s := "${numbers:2} "
println(s[1 .. s.len-2])
}
}</lang>
{{out}}
<pre>
Same as go entry
</pre>
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