Create First_Bad_Version.java

Author: 17tanya

BinarySearch/First_Bad_Version.java

@@ -0,0 +1,63 @@
+//Leetcode 278. First Bad Version
+//Question - https://leetcode.com/problems/first-bad-version/
+
+/*You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.
+
+Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be bad.
+
+You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.
+
+Example:
+
+Given n = 5, and version = 4 is the first bad version.
+
+call isBadVersion(3) -> false
+call isBadVersion(5) -> true
+call isBadVersion(4) -> true
+
+Then 4 is the first bad version.*/
+
+/* The isBadVersion API is defined in the parent class VersionControl.
+      boolean isBadVersion(int version); */
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        int low = 1;
+        int high = n;
+        
+        while(low < high){
+            int mid = low + (high-low)/2;
+            boolean isBad = isBadVersion(mid);
+            
+            if(isBad){
+                high = mid;
+            }
+            else low = mid + 1;
+        }
+        
+        return low;
+    }
+}
+
+//OR
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        int low = 1;
+        int high = n;
+        int result = -1;
+        
+        while(low<=high){
+            int mid = low + (high-low)/2;
+            boolean isBad = isBadVersion(mid);
+            
+            if(isBad){
+                result = mid;
+                high = mid-1;
+            }
+            else low = mid + 1;
+        }
+        
+        return result;
+    }
+}