Create Day 1 First Bad Version.cpp

Author: tusharjaiswal123

Day 1 First Bad Version.cpp

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+PROBLEM:
+
+
+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. 
+
+
+SOLUTION:
+
+
+// The API isBadVersion is defined for you.
+// bool isBadVersion(int version);
+
+class Solution {
+public:
+    int firstBadVersion(int n) {        
+        int ans,l,h,m;
+        l=1;
+        h=n;
+        
+        while(l<=h)                       ////lower bound binary search
+        {
+            m=l+(h-l)/2;
+            
+            if(isBadVersion(m))
+            {
+                ans=m;
+                h=m-1;
+            }
+            else
+            {
+                l=m+1;
+            }
+        }
+        
+        return ans;
+        
+        
+    }
+};