first bad version

firstBadVersion/main.go

@@ -0,0 +1,26 @@
+package main
+
+func isBadVersion(version int) bool
+
+/**
+ * Forward declaration of isBadVersion API.
+ * @param   version   your guess about first bad version
+ * @return 	 	      true if current version is bad
+ *			          false if current version is good
+ * func isBadVersion(version int) bool;
+ */
+
+func firstBadVersion(n int) int {
+	left := 0
+	right := n
+	for left < right {
+		mid := (right-left)/2 + left
+		// isBad := isBadVersion(mid)
+		if isBadVersion(mid) {
+			right = mid
+		} else {
+			left = mid + 1
+		}
+	}
+	return left
+}