v/examples/quick_sort.v

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import rand
const (
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gen_len = 1000 // how many random numbers to generate
gen_max = 10000 // max of the generated numbers
)
fn main() {
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mut arr := []int{}
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for _ in 0 .. gen_len {
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arr << rand.intn(gen_max)
}
println('length of random array is $arr.len')
println('before quick sort whether array is sorted: ${is_sorted<int>(arr)}')
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quick_sort<int>(mut arr, 0, arr.len - 1)
println('after quick sort whether array is sorted: ${is_sorted<int>(arr)}')
}
fn quick_sort<T>(mut arr []T, l int, r int) {
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if l >= r {
return
}
mut sep := l // what is sep: [...all_value<arr[sep]...sep...all_value>=arr[sep]...]
for i in l + 1 .. r + 1 {
if arr[i] < arr[l] {
sep++
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arr[i], arr[sep] = arr[sep], arr[i]
}
}
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arr[l], arr[sep] = arr[sep], arr[l]
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quick_sort<T>(mut arr, l, sep - 1)
quick_sort<T>(mut arr, sep + 1, r)
}
fn is_sorted<T>(arr []T) bool {
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for i in 0 .. arr.len - 1 {
if arr[i] > arr[i + 1] {
return false
}
}
return true
}