feat: Add Valid Parentheses problem in C++

c++ problems asked in interview/Valid_Parentheses.cpp

@@ -0,0 +1,66 @@
+/*
+* C++ Solution for the "Valid Parentheses" Problem
+*
+* Problem: Given a string s containing just the characters '(', ')',
+* '{', '}', '[' and ']', determine if the input string is valid.
+* An input string is valid if:
+* 1. Open brackets must be closed by the same type of brackets.
+* 2. Open brackets must be closed in the correct order.
+*
+* Contributor: Priyanka Anand
+* Submitted for Hacktoberfest 2025
+*/
+
+#include <iostream>
+#include <string>
+#include <stack>
+#include <unordered_map>
+
+class Solution {
+public:
+    bool isValid(std::string s) {
+        std::stack<char> charStack;
+        // Map to hold the valid pairs
+        std::unordered_map<char, char> pairs = {
+            {')', '('},
+            {']', '['},
+            {'}', '{'}
+        };
+
+        for (char c : s) {
+            // If it's a closing bracket
+            if (pairs.count(c)) {
+                // Check if stack is empty or top element doesn't match
+                if (charStack.empty() || charStack.top() != pairs[c]) {
+                    return false; // Invalid
+                }
+                charStack.pop(); // It's a valid pair, pop the opening bracket
+            } else {
+                // It's an opening bracket, push onto stack
+                charStack.push(c);
+            }
+        }
+
+        // If the stack is empty, all brackets were matched
+        return charStack.empty();
+    }
+};
+
+// Main function to test the solution
+int main() {
+    Solution sol;
+    std::string str1 = "()[]{}";
+    std::string str2 = "([)]";
+    std::string str3 = "{[]}";
+
+    std::cout << "String \"" << str1 << "\" is valid: " 
+              << (sol.isValid(str1) ? "true" : "false") << std::endl;
+
+    std::cout << "String \"" << str2 << "\" is valid: " 
+              << (sol.isValid(str2) ? "true" : "false") << std::endl;
+
+    std::cout << "String \"" << str3 << "\" is valid: " 
+              << (sol.isValid(str3) ? "true" : "false") << std::endl;
+
+    return 0;
+}