Add FirstBadVersion.java

Author: tinycedar

FirstBadVersion.java

@@ -0,0 +1,37 @@
+import java.text.MessageFormat;
+
+/**
+ * 
+ */
+
+/**
+ * @author qienl
+ *
+ */
+public class FirstBadVersion {
+
+	public int firstBadVersion(int n) {
+		return doFind(1, n);
+	}
+
+	private int doFind(int begin, int end) {
+		int middle = Long.valueOf((Long.valueOf(end) + Long.valueOf(begin)) / 2).intValue();
+//		System.out.println(MessageFormat.format("[{0}, {1}]\t{2}", begin, end, middle));
+		if (end - begin <= 1) {
+			return isBadVersion(begin) ? begin : end;
+		}
+		if (isBadVersion(middle)) {
+			return doFind(begin, middle);
+		} else {
+			return doFind(middle + 1, end);
+		}
+	}
+
+	private boolean isBadVersion(int n) {
+		return n >= 1702766719;
+	}
+
+	public static void main(String[] args) {
+		System.out.println(new FirstBadVersion().firstBadVersion(2126753390));
+	}
+}