Add an implementation of Selection Sort

src/Index.re

@@ -3,4 +3,8 @@ let expected_list = [1, 2, 3, 4, 5, 6, 7, 8, 9];
 
 let sorted_list = InsertionSort.sort(unsorted_list);
 
-Invariant.expect(sorted_list == expected_list);
+Invariant.expect(sorted_list == expected_list);
+
+let sorted_list_2 = SelectionSort.sort(unsorted_list);
+
+Invariant.expect(sorted_list_2 == expected_list);

src/SelectionSort.re

@@ -0,0 +1,62 @@
+/*
+ Selection Sort
+ https://en.wikipedia.org/wiki/Selection_sort
+
+ /* a[0] to a[n-1] is the array to sort */
+ int i,j;
+ int n;
+
+ /* advance the position through the entire array */
+ /*   (could do j < n-1 because single element is also min element) */
+ for (j = 0; j < n-1; j++)
+ {
+     /* find the min element in the unsorted a[j .. n-1] */
+
+     /* assume the min is the first element */
+     int iMin = j;
+     /* test against elements after j to find the smallest */
+     for (i = j+1; i < n; i++)
+     {
+         /* if this element is less, then it is the new minimum */
+         if (a[i] < a[iMin])
+         {
+             /* found new minimum; remember its index */
+             iMin = i;
+         }
+     }
+
+     if (iMin != j)
+     {
+         swap(a[j], a[iMin]);
+     }
+ }
+ */
+
+let sort = (items: list(int)) : list(int) => {
+  let j = ref(0);
+  let len = List.length(items);
+  let swappable_items = ref(items);
+
+  while (j^ < len - 1) {
+    let iMin = ref(j^);
+    let i = ref(j^ + 1);
+
+    while (i^ < len) {
+      let iValue = List.nth(swappable_items^, i^);
+      let iMinValue = List.nth(swappable_items^, iMin^);
+      if (iValue < iMinValue) {
+        iMin := i^;
+      };
+
+      i := i^ + 1;
+    };
+
+    if (iMin^ != j^) {
+      swappable_items := Util.swap(swappable_items^, j^, iMin^);
+    };
+
+    j := j^ + 1;
+  };
+
+  swappable_items^;
+};