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- #!/usr/bin/ruby
- #
- ## https://rosettacode.org/wiki/Quickselect_algorithm
- #
- func quickselect(a, k) {
- var pivot = a.pick;
- var left = a.grep{|i| i < pivot};
- var right = a.grep{|i| i > pivot};
-
- given(var l = left.len) {
- when(k) { pivot }
- case(k < l) { __FUNC__(left, k) }
- default { __FUNC__(right, k - l - 1) }
- }
- }
-
- var v = [9, 8, 7, 6, 5, 0, 1, 2, 3, 4];
- var arr = v.range.map{|i| quickselect(v, i)};
- say arr;
- assert_eq(arr, v.sort);
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