Data commit

Task/Binary-search/C/binary-search.c

@@ -0,0 +1,52 @@
+#include <stdio.h>
+
+int bsearch (int *a, int n, int x) {
+    int i = 0, j = n - 1;
+    while (i <= j) {
+        int k = i + ((j - i) / 2);
+        if (a[k] == x) {
+            return k;
+        }
+        else if (a[k] < x) {
+            i = k + 1;
+        }
+        else {
+            j = k - 1;
+        }
+    }
+    return -1;
+}
+
+int bsearch_r (int *a, int x, int i, int j) {
+    if (j < i) {
+        return -1;
+    }
+    int k = i + ((j - i) / 2);
+    if (a[k] == x) {
+        return k;
+    }
+    else if (a[k] < x) {
+        return bsearch_r(a, x, k + 1, j);
+    }
+    else {
+        return bsearch_r(a, x, i, k - 1);
+    }
+}
+
+int main () {
+    int a[] = {-31, 0, 1, 2, 2, 4, 65, 83, 99, 782};
+    int n = sizeof a / sizeof a[0];
+    int x = 2;
+    int i = bsearch(a, n, x);
+    if (i >= 0)
+      printf("%d is at index %d.\n", x, i);
+    else
+      printf("%d is not found.\n", x);
+    x = 5;
+    i = bsearch_r(a, x, 0, n - 1);
+    if (i >= 0)
+      printf("%d is at index %d.\n", x, i);
+    else
+      printf("%d is not found.\n", x);
+    return 0;
+}