{"id":7688,"date":"2025-07-09T10:20:13","date_gmt":"2025-07-09T04:50:13","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7688"},"modified":"2025-09-26T16:44:12","modified_gmt":"2025-09-26T11:14:12","slug":"valid-parentheses","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/valid-parentheses\/","title":{"rendered":"Valid Parentheses"},"content":{"rendered":"\n<!-- PrismJS for Syntax Highlighting -->\n<link href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.min.css\" rel=\"stylesheet\">\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/prism.min.js\"><\/script>\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/plugins\/autoloader\/prism-autoloader.min.js\"><\/script>\n\n<style>\n.wp_blog_theme {\n  --primary: #E58C32;\n  --secondary: #030302;\n  --light-bg: #fef9f4;\n  --text-dark: #2d2d2d;\n  --tab-radius: 12px;\n  --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);\n  --code-bg: #001f3f;\n  --code-text: #d4f1ff;\n}\n\n.wp_blog_container {\n  font-family: 'Segoe UI', sans-serif;\n  background: var(--light-bg);\n  margin: 0;\n  padding: 0;\n  color: var(--text-dark);\n}\n\n\/* Heading *\/\n.wp_blog_main-heading {\n  text-align: center;\n  font-size: 2.4rem;\n  color: var(--primary);\n  margin-top: 2.5rem;\n  font-weight: bold;\n}\n\n\/* Explanation Card *\/\n.wp_blog_explanation,\n.wp_blog_code-tabs-container {\n  max-width: 940px;\n  margin: 2rem auto;\n  padding: 2rem;\n  background: white;\n  border-radius: var(--tab-radius);\n  box-shadow: var(--shadow);\n}\n\n\/* Text and Visuals *\/\n.wp_blog_explanation h2 {\n  font-size: 1.4rem;\n  color: var(--primary);\n  margin-bottom: 0.5rem;\n}\n\n.wp_blog_explanation p,\n.wp_blog_explanation li {\n  font-size: 1.05rem;\n  line-height: 1.7;\n  margin: 0.5rem 0;\n}\n\n.wp_blog_explanation code {\n  background: #fef9f4; 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\/* makes it the reference for absolute children *\/\n}\n\n.wp_blog_toggle-btn {\n  position: absolute;\n  top: 1rem;\n  right: 1rem;\n  z-index: 9999;\n  padding: 0.5rem 0.8rem;\n  border-radius: 10%;\n  background: var(--primary);\n  color: white;\n  font-weight: bold;\n  cursor: pointer;\n  border: none;\n  box-shadow: var(--shadow);\n  transition: background 0.3s, transform 0.2s;\n}\n\n.wp_blog_toggle-btn:hover {\n  background: #cc772e;\n}\n\n.wp_blog_theme.dark-mode .wp_blog_code-tabs-container {\n  background: #1e1e1e;\n}\n<\/style>\n\n<div class=\"wp_blog_container wp_blog_theme\">\n  <button id=\"blogNotesThemeToggle\" class=\"wp_blog_toggle-btn\">\ud83c\udf19<\/button>\n  <h1 class=\"wp_blog_main-heading\"><\/h1>\n\n  <div class=\"wp_blog_explanation\">\n    <h2>Problem Statement:<\/h2>\n    <p>\n        Given a string s containing just the characters <code>'('<\/code>, &#8216;)&#8217;, &#8216;{&#8216;, &#8216;}&#8217;, &#8216;[&#8216; and &#8216;]&#8217;, determine if the input string is valid.\n    <\/p>\n\n    <p>\n        An input string is valid if:\n    <\/p>\n\n    <ul>\n        <li>Open brackets must be closed by the same type of brackets.<\/li>\n        <li>Open brackets must be closed in the correct order.<\/li>\n        <li>Every close bracket has a corresponding open bracket of the same type.<\/li>\n    <\/ul>\n\n    <h3>Example 1:<\/h2>\n    <p><strong>Input:<\/strong> s = &#8220;()&#8221;<\/p>\n    <p><strong>Output:<\/strong> true<\/p>\n\n    <h3>Example 2:<\/h2>\n    <p><strong>Input:<\/strong> s = &#8220;()[]{}&#8221;<\/p>\n    <p><strong>Output:<\/strong> true<\/p>\n\n    <p>Example 3:<\/p>\n    <p><strong>Input:<\/strong> s = &#8220;(]&#8221;<\/p>\n    <p><strong>Output:<\/strong> false<\/p>\n\n    <p>Example 4:<\/p>\n    <p><strong>Input:<\/strong>  s = &#8220;([])&#8221;<\/p>\n    <p><strong>Output:<\/strong> true<\/p>\n\n    <p>Example 5:<\/p>\n    <p><strong>Input:<\/strong> s = &#8220;([)]&#8221;<\/p>\n    <p><strong>Output:<\/strong> false<\/p>\n\n    <h2>Constraints:<\/h2>\n    <ul>\n        <li><code>1<= s.length <= 10<sup>4<\/sup><\/code><\/li>\n        <li><code>s<\/code> consists of parentheses only <code>'()[]{}'<\/code>.<\/li>\n    <\/ul>\n    \n<h2>Approach:<\/h2>\n<ul>\n    <li>Use a <strong>stack<\/strong> to track opening brackets.<\/li>\n    <li>Create a <strong>map<\/strong> that stores matching pairs \u2192 <code>{ : }, [ : ], ( : )<\/code>.<\/li>\n    <li>Traverse the string:\n        <ul>\n            <li>If it&#8217;s an <strong>opening bracket<\/strong>, push it onto the stack.<\/li>\n            <li>If it&#8217;s a <strong>closing bracket<\/strong>, pop from the stack and check if it matches the expected closing bracket. If not, <code>return false<\/code>.<\/li>\n        <\/ul>\n    <\/li>\n    <li>After processing, if the stack is empty \u2192 all brackets matched \u2192 <code>return true<\/code>. Otherwise, <code>return false<\/code>.<\/li>\n<\/ul>\n\n    <h2>Time &#038; Space Complexity:<\/h2>\n    <p><strong>Time Complexity:<\/strong> <code>O(n)<\/code><\/p>\n    <p><strong>Space Complexity:<\/strong> <code>O(n)<\/code><\/p>\n\n<h2>Dry Run<\/h2>\n<div style=\"background: var(--light-bg); border-left: 4px solid var(--primary); padding: 1rem; border-radius: var(--tab-radius); margin: 1rem 0; color: var(--text-dark);\"> \n  <p><strong>Input:<\/strong> <code>s = \"([{}])\"<\/code><\/p> \n  \n  <pre style=\"white-space: pre-wrap; background: var(--code-bg); padding: 1rem; border-radius: 8px; overflow-x: auto; color: var(--code-text);\">\n\nStep 0: Start Function isValid(\"([{}])\")\nstack = []\nmap = { \"{\" : \"}\", \"[\" : \"]\", \"(\" : \")\" }\n\nIteration (i = 0): s[0] = \"(\"\n- \"(\" is in map \u2192 push to stack\n- stack = [\"(\"]\n\nIteration (i = 1): s[1] = \"[\"\n- \"[\" is in map \u2192 push to stack\n- stack = [\"(\", \"[\"]\n\nIteration (i = 2): s[2] = \"{\"\n- \"{\" is in map \u2192 push to stack\n- stack = [\"(\", \"[\", \"{\"]\n\nIteration (i = 3): s[3] = \"}\"\n- \"}\" is not in map \u2192 pop from stack\n- top = \"{\"\n- Check s[3] == map[top] \u2192 \"}\" == map[\"{\"] \u2192 \"}\" == \"}\" \u2714\n- stack = [\"(\", \"[\"]\n\nIteration (i = 4): s[4] = \"]\"\n- \"]\" is not in map \u2192 pop from stack\n- top = \"[\"\n- Check s[4] == map[top] \u2192 \"]\" == map[\"[\"] \u2192 \"]\" == \"]\" \u2714\n- stack = [\"(\"]\n\nIteration (i = 5): s[5] = \")\"\n- \")\" is not in map \u2192 pop from stack\n- top = \"(\"\n- Check s[5] == map[top] \u2192 \")\" == map[\"(\"] \u2192 \")\" == \")\" \u2714\n- stack = []\n\nLoop ends (i == s.length)\n\nFinal Check:\nstack.length === 0 \u2192 true\nReturn true\n  <\/pre> \n  \n  <p><strong>Output:<\/strong> <code>true<\/code><\/p> \n<\/div>\n\n <!-- <h2>Visualisation:<\/h2>\n    <img decoding=\"async\"\n        src=\"https:\/\/namastedev.com\/blog\/wp-content\/uploads\/2025\/07\/Screenshot-2025-07-09-at-10.14.16\u202fAM.png\"\n        alt=\"valid\"\n    \/> -->\n<\/div>\n\n\n  <div class=\"wp_blog_code-tabs-container\">\n    <div class=\"wp_blog_code-tabs-header\">\n      <button class=\"wp_blog_code-tab-button active\" data-lang=\"js\">JavaScript<\/button>\n      <button class=\"wp_blog_code-tab-button\" data-lang=\"py\">Python<\/button>\n      <button class=\"wp_blog_code-tab-button\" data-lang=\"java\">Java<\/button>\n      <button class=\"wp_blog_code-tab-button\" data-lang=\"cpp\">C++<\/button>\n      <button class=\"wp_blog_code-tab-button\" data-lang=\"c\">C<\/button>\n      <button class=\"wp_blog_code-tab-button\" data-lang=\"cs\">C#<\/button>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n      <pre><code class=\"language-javascript\">\nvar isValid = function(s){\n    let stack = [];\n\n    let map = {\n        \"{\" : \"}\",\n        \"[\" : \"]\",\n        \"(\" : \")\"\n    }\n\n    for(let i=0; i < s.length; i++){\n        if(map[s[i]]) {\n            stack.push(s[i]);\n        }\n        else {\n            let top = stack.pop();\n            if(!top || s[i] != map[top]) {\n                return false;\n            }\n        }\n    }\n    return stack.length === 0;\n}\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n      <pre><code class=\"language-python\">\ndef isValid(s: str) -> bool:\n    stack = []\n    pairs = {'{': '}', '[': ']', '(': ')'}\n\n    for ch in s:\n        if ch in pairs:\n            stack.append(ch)\n        else:\n            if not stack:\n                return False\n            top = stack.pop()\n            if ch != pairs[top]:\n                return False\n    return len(stack) == 0\n      <\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n      <pre><code class=\"language-java\">\nimport java.util.HashMap;\nimport java.util.Map;\nimport java.util.Stack;\n\npublic class Solution {\n    public boolean isValid(String s) {\n        Stack<Character> stack = new Stack<>();\n        Map<Character, Character> map = new HashMap<>();\n        map.put('{', '}');\n        map.put('[', ']');\n        map.put('(', ')');\n\n        for (int i = 0; i < s.length(); i++) {\n            char c = s.charAt(i);\n            if (map.containsKey(c)) {\n                stack.push(c);\n            } else {\n                if (stack.isEmpty()) return false;\n                char top = stack.pop();\n                if (c != map.get(top)) return false;\n            }\n        }\n        return stack.isEmpty();\n    }\n}\n\n    <\/code><\/pre>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cpp\">\n      <pre><code class=\"language-cpp\">\n#include &lt;string&gt;\n#include &lt;vector&gt;\n#include &lt;unordered_map&gt;\n\nbool isValid(const std::string &s) {\n    std::vector<char> stack;\n    std::unordered_map<char,char> map = {\n        {'{', '}'},\n        {'[', ']'},\n        {'(', ')'}\n    };\n\n    for (char c : s) {\n        if (map.count(c)) {\n            stack.push_back(c);\n        } else {\n            if (stack.empty()) return false;\n            char top = stack.back();\n            stack.pop_back();\n            if (c != map[top]) return false;\n        }\n    }\n    return stack.empty();\n}\n\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n      <pre><code class=\"language-c\">\n#include &lt;stdio.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;string.h&gt;\n\nint isValid(const char *s) {\n    size_t n = strlen(s);\n    char *stack = (char*)malloc(n + 1);\n    if (!stack) return 0; \/\/ allocation failed, treat as invalid\n    int topIndex = 0;\n\n    for (size_t i = 0; i < n; ++i) {\n        char c = s[i];\n        if (c == '{' || c == '[' || c == '(') {\n            stack[topIndex++] = c;\n        } else {\n            if (topIndex == 0) { free(stack); return 0; }\n            char top = stack[--topIndex];\n            if (!(\n                (top == '{' &#038;&#038; c == '}') ||\n                (top == '[' &#038;&#038; c == ']') ||\n                (top == '(' &#038;&#038; c == ')')\n            )) {\n                free(stack);\n                return 0;\n            }\n        }\n    }\n    int result = (topIndex == 0) ? 1 : 0;\n    free(stack);\n    return result;\n}\n <\/code><\/pre>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n      <pre><code class=\"language-csharp\">\nusing System;\nusing System.Collections.Generic;\n\npublic class Solution {\n    public bool IsValid(string s) {\n        var stack = new Stack<char>();\n        var map = new Dictionary<char, char> {\n            {'{', '}'},\n            {'[', ']'},\n            {'(', ')'}\n        };\n\n        foreach (char c in s) {\n            if (map.ContainsKey(c)) {\n                stack.Push(c);\n            } else {\n                if (stack.Count == 0) return false;\n                char top = stack.Pop();\n                if (c != map[top]) return false;\n            }\n        }\n        return stack.Count == 0;\n    }\n}\n      <\/code><\/pre>\n    <\/div>\n  <\/div>\n<\/div>\n\n<script>\ndocument.addEventListener(\"DOMContentLoaded\", () => {\n  const buttons = document.querySelectorAll(\".wp_blog_code-tab-button\");\n  const contents = document.querySelectorAll(\".wp_blog_code-tab-content\");\n\n  buttons.forEach((button) => {\n    button.addEventListener(\"click\", () => {\n      const lang = button.getAttribute(\"data-lang\");\n\n      buttons.forEach((btn) => btn.classList.remove(\"active\"));\n      contents.forEach((content) => content.classList.remove(\"active\"));\n\n      button.classList.add(\"active\");\n      document\n        .querySelector(`.wp_blog_code-tab-content[data-lang=\"${lang}\"]`)\n        .classList.add(\"active\");\n    });\n  });\n\n  const themeToggle = document.getElementById(\"blogNotesThemeToggle\");\n  const themeContainer = document.querySelector(\".wp_blog_theme\");\n\n  themeToggle.addEventListener(\"click\", () => {\n    themeContainer.classList.toggle(\"dark-mode\");\n    themeToggle.textContent =\n      themeContainer.classList.contains(\"dark-mode\") ? \"\u2600\ufe0f\" : \"\ud83c\udf19\";\n  });\n});\n<\/script>\n\n","protected":false},"excerpt":{"rendered":"<p>\ud83c\udf19 Problem Statement: Given a string s containing just the characters &#8216;(&#8216;, &#8216;)&#8217;, &#8216;{&#8216;, &#8216;}&#8217;, &#8216;[&#8216; and &#8216;]&#8217;, determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has<\/p>\n","protected":false},"author":108,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[322,260,176,175,211,810,174,172,173],"tags":[],"class_list":["post-7688","post","type-post","status-publish","format-standard","category-algorithms-and-data-structures","category-c-c-plus-plus","category-csharp","category-cplusplus","category-data-structures","category-dsa","category-java","category-javascript","category-python"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7688","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/users\/108"}],"replies":[{"embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/comments?post=7688"}],"version-history":[{"count":3,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7688\/revisions"}],"predecessor-version":[{"id":10138,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7688\/revisions\/10138"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7688"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7688"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7688"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}