Merge pull request neetcode-gh#3288 from adityaiiitr/backtracking

create 1980-find-unique-binary-string.cpp

Author: a93a

cpp/1980-find-unique-binary-string.cpp

@@ -0,0 +1,51 @@
+/*
+    This class implements a solution to find a binary string that differs from a given list of binary strings.
+    
+    Approach:
+    1. Define a backtrack function to explore all possible binary strings of the same length as the input strings.
+    2. Use a set to store the input strings to efficiently check for duplicates.
+    3. Backtrack through all possible binary strings of length equal to the input strings.
+    4. If a binary string is found that does not exist in the set of input strings, update the result and return.
+    
+    Variables:
+    - result: Holds the result, initialized to an empty string.
+    - backtrack(): Recursive function to generate binary strings and check for uniqueness.
+    - inputStrings: Input vector of binary strings.
+    - currentString: Current binary string being constructed during backtracking.
+    - stringLength: Length of binary strings in the input.
+    - stringSet: Set to store input binary strings for fast duplicate checking.
+
+    Time Complexity: O(2^N * N), where N is the length of the binary strings.
+        - The function 'backtrack' explores all possible binary strings of length N, which is O(2^N).
+        - Checking for uniqueness in the set takes O(1) time on average.
+    Space Complexity: O(2^N * N) considering the space required to store the generated binary strings during backtracking.
+*/
+
+class Solution {
+public:
+    string result = "";
+    
+    void backtrack(vector<string>& inputStrings, string& currentString, int stringLength, set<string>& stringSet) {
+        if (!result.empty()) return;
+        if (currentString.size() == stringLength && stringSet.find(currentString) == stringSet.end()) {
+            result = currentString;
+            return;
+        }
+        if (currentString.size() > stringLength) return;
+
+        for (char ch = '0'; ch <= '1'; ++ch) {
+            currentString.push_back(ch);
+            backtrack(inputStrings, currentString, stringLength, stringSet);
+            currentString.pop_back();
+        }
+    }
+    
+    string findDifferentBinaryString(vector<string>& inputStrings) {
+        int stringLength = inputStrings[0].size();
+        string currentString = "";
+        set<string> stringSet(inputStrings.begin(), inputStrings.end());
+
+        backtrack(inputStrings, currentString, stringLength, stringSet);
+        return result;
+    }
+};