From 995ce4e0e02e0eb33874fe29779a5ed067aa0a56 Mon Sep 17 00:00:00 2001
From: Tatheer Fathima <148070120+T-Fathima@users.noreply.github.com>
Date: Sat, 2 Nov 2024 15:54:07 +0000
Subject: [PATCH] Added Balanced Paranthesis

---
 docs/Stack/Balanced-Parenthesis.md | 106 +++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 docs/Stack/Balanced-Parenthesis.md

diff --git a/docs/Stack/Balanced-Parenthesis.md b/docs/Stack/Balanced-Parenthesis.md
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+---
+id: balanced-parentheses
+title: Balanced Parentheses
+sidebar_label: Balanced Parentheses
+description: "The Balanced Parentheses problem involves determining whether a given string of parentheses is valid, meaning every opening bracket has a corresponding closing bracket in the correct order."
+tags: [dsa, algorithms, stack]
+---
+
+### Definition:
+The Balanced Parentheses problem is a classic problem in computer science that checks if a string containing parentheses is valid. A string is considered valid if every opening parenthesis has a corresponding closing parenthesis and they are properly nested.
+
+### Problem Statement:
+Given a string `s` consisting of parentheses (i.e., `(`, `)`, `{`, `}`, `[`, `]`), determine if the input string is valid. An input string is valid if:
+- Open brackets are closed by the same type of brackets.
+- Open brackets are closed in the correct order.
+
+### Algorithm Steps:
+
+1. **Initialize a Stack:** Use a stack to keep track of opening parentheses.
+2. **Iterate through the string:** For each character in the string:
+   - If it is an opening bracket, push it onto the stack.
+   - If it is a closing bracket, check if the stack is not empty and the top of the stack is the corresponding opening bracket; if so, pop the stack. If not, return false.
+3. **Final Check:** After processing all characters, if the stack is empty, return true (all brackets are matched); otherwise, return false.
+
+### Steps Involved:
+**1. Stack Structure:**
+   - Use a stack data structure to store opening brackets.
+
+**2. Functions:**
+   - `isValid(s: str) -> bool:` Checks if the parentheses in the string are balanced.
+
+### Time Complexity:
+- The time complexity of the `isValid` function is `O(n)`, where `n` is the length of the string. This is because we scan through the string once, and each push/pop operation on the stack takes constant time.
+
+### Space Complexity:
+- The space complexity is `O(n)` in the worst case, where all characters in the string are opening brackets, and they are stored in the stack.
+
+### Sample Input:
+"()" "()[]{}" "(]" "([)]" "{[]}"
+
+### Sample Output:
+true true false false true
+
+### Explanation of Sample:
+- The input strings are evaluated for balanced parentheses.
+- `()`, `()[]{}`, and `{[]}` are valid, while `(]` and `([)]` are not, due to mismatched or improperly nested brackets.
+
+### Python Implementation:
+
+```python
+def isValid(s: str) -> bool:
+    stack = []
+    mapping = {")": "(", "}": "{", "]": "["}
+
+    for char in s:
+        if char in mapping:
+            top_element = stack.pop() if stack else '#'
+            if mapping[char] != top_element:
+                return False
+        else:
+            stack.append(char)
+
+    return not stack
+
+# Sample Test Cases
+test_cases = ["()", "()[]{}", "(]", "([)]", "{[]}"]
+for case in test_cases:
+    print(f"{case}: {isValid(case)}")
+
+```
+
+### C++ Implementation:
+```cpp
+#include <iostream>
+#include <stack>
+#include <unordered_map>
+using namespace std;
+
+bool isValid(string s) {
+    stack<char> stack;
+    unordered_map<char, char> mapping = {{')', '('}, {'}', '{'}, {']', '['}};
+
+    for (char &c : s) {
+        if (mapping.count(c)) {
+            char top_element = stack.empty() ? '#' : stack.top();
+            stack.pop();
+            if (mapping[c] != top_element) {
+                return false;
+            }
+        } else {
+            stack.push(c);
+        }
+    }
+
+    return stack.empty();
+}
+
+// Sample Test Cases
+int main() {
+    string test_cases[] = {"()", "()[]{}", "(]", "([)]", "{[]}"};
+    for (const string& case : test_cases) {
+        cout << case << ": " << (isValid(case) ? "true" : "false") << endl;
+    }
+    return 0;
+}
+```