Update all new Tasks

Task/Quickselect-algorithm/J/quickselect-algorithm-1.j

@@ -0,0 +1,14 @@
+quickselect=:4 :0
+  if. 0=#y do. _ return. end.
+  n=.?#y
+  m=.n{y
+  if. x < m do.
+    x quickselect (m>y)#y
+  else.
+    if. x > m do.
+      x quickselect (m<y)#y
+    else.
+      m
+    end.
+  end.
+)

Task/Quickselect-algorithm/J/quickselect-algorithm-2.j

@@ -0,0 +1,2 @@
+   8 quickselect 9, 8, 7, 6, 5, 0, 1, 2, 3, 4
+8

Task/Quickselect-algorithm/J/quickselect-algorithm-3.j

@@ -0,0 +1,2 @@
+   ((10 {./:~) quickselect"0 1 ]) 9, 8, 7, 6, 5, 0, 1, 2, 3, 4
+0 1 2 3 4 5 6 7 8 9