Add examples on scheme. Chapters: 1, 2 (#258)

* add  01_binary_search.scm in 01_introduction_to_algorithms

* any fix

* add 01_selection_sort.scm to 02_selection_sort

* any fix

01_introduction_to_algorithms/scheme/01_binarysearch.scm

@@ -0,0 +1,14 @@
+(define (binary-search my-list item)
+  (iter my-list item 0 (- (length my-list) 1)))
+
+(define (iter my-list item low high)
+  (if (> low high) 'nill
+    (let* ((mid (floor (/ (+ low high) 2)))
+          (guess (list-ref my-list mid)))
+      (cond ((eqv? guess item) mid)
+              ((> guess item) (iter my-list item low (- mid 1)))
+              (else (iter my-list item (+ mid 1) high))))))
+
+
+(display (binary-search (list 1 3 5 7 9) 3)) ;; 1
+(display (binary-search (list 1 3 5 7 9) -1)) ;; nill

02_selection_sort/scheme/01_selection_sort.scm

@@ -0,0 +1,37 @@
+(define (find-smallest my-list)
+  (let ((smallest (list-ref my-list 0))
+        (smallest-i 0)
+        (i 0)
+        (last-index (- (length my-list) 1)))
+    (iter-find my-list smallest-i smallest i last-index)))
+
+(define (iter-find my-list smallest-i smallest i last-index)
+  (if (> i last-index) 
+      smallest-i
+      (let ((my-list-i (list-ref my-list i)))
+        (if (< my-list-i smallest)
+            (iter-find my-list i my-list-i (+ i 1) last-index)
+            (iter-find my-list smallest-i smallest (+ i 1) last-index)))))
+
+
+(define (selection-sort my-list)
+  (let* ((my-list-length (length my-list))
+        (result (list))
+        (i 0)
+        (last-i (- my-list-length 1)))
+    (iter-sort my-list i last-i result)))
+
+(define (iter-sort my-list i last-i result)
+  (if (> i last-i)
+      result
+      (let* ((smallest-i (find-smallest my-list))
+            (smallest (list-ref my-list smallest-i))
+            (filtered-list (filter (lambda (n) (not (= n smallest)))
+                                   my-list))
+            (new-result (append result (list smallest))))
+        (iter-sort filtered-list (+ i 1) last-i new-result))))
+
+
+(display (selection-sort (list 1 3 5 7 9))) ;; #(1 3 5 7 9)
+(display (selection-sort (list 9 7 5 3 1))) ;; #(1 3 5 7 9)
+(display (selection-sort (list 9 5 7 1 3))) ;; #(1 3 5 7 9)