{"id":7925,"date":"2025-07-16T09:57:28","date_gmt":"2025-07-16T04:27:28","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7925"},"modified":"2025-07-16T11:53:47","modified_gmt":"2025-07-16T06:23:47","slug":"firstoccurrence","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/firstoccurrence\/","title":{"rendered":"Find Index of First Occurrence in String"},"content":{"rendered":"\n<link\n    href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.min.css\"\n    rel=\"stylesheet\"\n\/>\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: #f8c291;\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.wp_blog_explanation h5{\n  color: var(--primary);\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.wp_blog_explanation code {\n  background: #f9cea6;\n  color: #2d2d2d;\n  padding: 3px 6px;\n  border-radius: 4px;\n  font-family: 'Courier New', monospace;\n}\n.wp_blog_explanation img {\n  max-width: 100%;\n  border-radius: var(--tab-radius);\n  margin-top: 1rem;\n  box-shadow: 0 2px 12px rgba(0,0,0,0.06);\n}\n\n\/* Tab Buttons *\/\n.wp_blog_code-tabs-header {\n  display: flex;\n  flex-wrap: wrap;\n  gap: 0.5rem;\n  margin-bottom: 1rem;\n}\n.wp_blog_code-tab-button {\n  padding: 0.6rem 1.2rem;\n  border: 1px solid var(--primary);\n  background: white;\n  color: var(--primary);\n  border-radius: 50px;\n  font-weight: 600;\n  cursor: pointer;\n  transition: all 0.3s ease;\n}\n.wp_blog_code-tab-button:hover {\n  background: var(--secondary);\n}\n.wp_blog_code-tab-button.active {\n  background: var(--primary);\n  color: white;\n}\n\n\/* Code Content *\/\n.wp_blog_code-tab-content {\n  display: none;\n  background: var(--code-bg);\n  border-radius: var(--tab-radius);\n}\n.wp_blog_code-tab-content.active {\n  display: block;\n}\n.wp_blog_code-tab-content pre {\n  margin: 0;\n  padding: 1.5rem;\n  font-size: 1rem;\n  overflow-x: auto;\n  background: var(--code-bg);\n  border-radius: var(--tab-radius);\n  color: var(--code-text);\n}\n<\/style>\n\n<div class=\"wp_blog_container wp_blog_theme\"> \n    <h1 class=\"wp_blog_main-heading\"><\/h1>\n    <div class=\"wp_blog_explanation\">\n        <h2>Problem Statement:<\/h2>\n\n        <p>Given two strings <code>needle<\/code> and <code>haystack<\/code>, return the index of the first occurrence of <code>needle<\/code> in <code>haystack<\/code>, or <code>-1<\/code> if <code>needle<\/code> is not part of <code>haystack<\/code>.\n        <\/p>\n\n                <h2>Examples:<\/h2>\n\n                <h5>Example 1:<\/h5>\n                <p><strong>Input:<\/strong>haystack = &#8220;sadbutsad&#8221;, needle = &#8220;sad&#8221;<\/p>\n                <p><strong>Output:<\/strong>0<\/p>\n                <p>\n                  <code>Explanation:<\/code>\n                  &#8220;sad&#8221; occurs at index 0 and 6.The first occurrence is at index 0, so we return 0.\n                <\/p>\n\n                <h5>Example 2:<\/h5>\n                <p><strong>Input:<\/strong>haystack = &#8220;leetcode&#8221;, needle = &#8220;leeto&#8221;<\/p>\n                <p><strong>Output:<\/strong>-1<\/p>\n                  <p>\n                  <code>Explanation:<\/code>\n                  &#8220;leeto&#8221; did not occur in &#8220;leetcode&#8221;, so we return -1.\n                <\/p>\n\n                    <h2>Constraints:<\/h2>\n                    <ul>\n                      <li><code>1 <= haystack.length, needle.length <= 10<sup>4<\/sup><\/code><\/li>\n                      <li><code>haystack<\/code> and <code>needle<\/code> consist of only lowercase English characters.<\/li>\n                    <\/ul>\n\n                <h2>Approach<\/h2>\n                <ul>\n                    <li>Loop through each index <code>i<\/code> in <code>haystack<\/code> where needle could start <code>(0 to n - m)<\/code>.<\/li>\n                    <li>For each <code>i<\/code>, compare needle with the substring starting at <code>i<\/code>.<\/li>\n                    <li>If all characters match, <code>return i<\/code>.<\/li>\n                    <li>If no match is found, <code>return -1<\/code>.<\/li>\n                <\/ul>\n\n                <h2>Time Complexity:<\/h2>\n                <li>\n                  <p><strong>Time Complexity = O(n * m)<\/strong>\n                  <\/li>\n                <h2>Space Complexity:<\/h2>\n                <li>\n                  <p><strong>Space Complexity = O(1)<\/strong><\/p>\n                <\/li>\n\n<h2>Dry Run<\/h2> <div style=\"background: #f9f9f9; border-left: 4px solid var(--primary); padding: 1rem; border-radius: var(--tab-radius); margin: 1rem 0;\"> <p><strong>Input:<\/strong> <code>haystack = \"hello\", needle = \"ll\"<\/code><\/p> <pre style=\"white-space: pre-wrap; background: #fff5ea; padding: 1rem; border-radius: 8px; overflow-x: auto;\"> n = 5, m = 2\ni = 0\nj = 0 \u2192 haystack[0 + 0] = 'h' \u2260 needle[0] = 'l' \u2192 break\n\ni = 1\nj = 0 \u2192 haystack[1 + 0] = 'e' \u2260 needle[0] = 'l' \u2192 break\n\ni = 2\nj = 0 \u2192 haystack[2 + 0] = 'l' == needle[0] = 'l'\nj = 1 \u2192 haystack[2 + 1] = 'l' == needle[1] = 'l'\n\u2192 j == m \u2192 return 2\n<\/pre>\n\n<p><strong>Output:<\/strong> <code>Result: 2<\/code><\/p> <\/div>\n                \n        <h2>Visualisation:<\/h2>\n        <img decoding=\"async\" src=\"https:\/\/namastedev.com\/blog\/wp-content\/uploads\/2025\/07\/Screenshot-2025-07-16-at-9.54.46\u202fAM.png\" alt=\"Stocks\" \/>\n    <\/div>\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        <!-- JavaScript -->\n        <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n            <pre><code class=\"language-javascript\">\nvar strStr = function(haystack, needle) {\n    let n = haystack.length;\n    let m = needle.length;\n\n    for (let i = 0; i <= n - m; i++) {\n        let j = 0;\n        for (j = 0; j < m; j++) {\n            if (haystack[i + j] !== needle[j]) {\n                break;\n            }\n        }\n        if (j === m) {\n            return i;\n        }\n    }\n    return -1;\n};\n     <\/code><\/pre>\n        <\/div>\n\n        <!-- Python -->\n        <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n            <pre><code class=\"language-python\">\ndef strStr(haystack, needle):\n    n = len(haystack)\n    m = len(needle)\n\n    for i in range(n - m + 1):\n        j = 0\n        for j in range(m):\n            if haystack[i + j] != needle[j]:\n                break\n        else:\n            return i\n    return -1\n\n            <\/code><\/pre>\n        <\/div>\n\n        <!-- Java -->\n        <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n            <pre><code class=\"language-java\">\nint strStr(String haystack, String needle) {\n    int n = haystack.length();\n    int m = needle.length();\n\n    for(int i = 0; i <= n - m; i++) {\n        int j = 0;\n        for(j = 0; j < m; j++) {\n            if(haystack.charAt(i + j) != needle.charAt(j)) {\n                break;\n            }\n        }\n        if(j == m) {\n            return i;\n        }\n    }\n    return -1;\n}       <\/code><\/pre>\n        <\/div>\n\n        <!-- C++ -->\n        <div class=\"wp_blog_code-tab-content\" data-lang=\"cpp\">\n            <pre><code class=\"language-cpp\">\nint strStr(string haystack, string needle) {\n    int n = haystack.length();\n    int m = needle.length();\n\n    for(int i = 0; i <= n - m; i++) {\n        int j = 0;\n        for(j = 0; j < m; j++) {\n            if(haystack[i + j] != needle[j]) {\n                break;\n            }\n        }\n        if(j == m) {\n            return i;\n        }\n    }\n    return -1;\n}   <\/code><\/pre>\n        <\/div>\n\n        <!-- C -->\n        <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n            <pre><code class=\"language-c\">\nint strStr(char* haystack, char* needle) {\n    int n = strlen(haystack);\n    int m = strlen(needle);\n\n    for(int i = 0; i <= n - m; i++) {\n        int j = 0;\n        for(j = 0; j < m; j++) {\n            if(haystack[i + j] != needle[j]) {\n                break;\n            }\n        }\n        if(j == m) {\n            return i;\n        }\n    }\n    return -1;\n}       <\/code><\/pre>\n        <\/div>\n\n        <!-- C# -->\n        <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n            <pre><code class=\"language-csharp\">\nint StrStr(string haystack, string needle) {\n    int n = haystack.Length;\n    int m = needle.Length;\n\n    for(int i = 0; i <= n - m; i++) {\n        int j = 0;\n        for(j = 0; j < m; j++) {\n            if(haystack[i + j] != needle[j]) {\n                break;\n            }\n        }\n        if(j == m) {\n            return i;\n        }\n    }\n    return -1;\n}\n        <\/code><\/pre>\n        <\/div>\n    <\/div>\n<\/div>\n\n<script>\n    document.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) =>\n                    content.classList.remove(\"active\")\n                );\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<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Problem Statement: Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Examples: Example 1: Input:haystack = &#8220;sadbutsad&#8221;, needle = &#8220;sad&#8221; Output:0 Explanation: &#8220;sad&#8221; occurs at index 0 and 6.The first occurrence is at index 0, so we return<\/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":[322,260,176,175,211,811,810,174,172,173],"tags":[],"class_list":["post-7925","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-data-structures-and-algorithms","category-dsa","category-java","category-javascript","category-python"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7925","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=7925"}],"version-history":[{"count":2,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7925\/revisions"}],"predecessor-version":[{"id":7927,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7925\/revisions\/7927"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7925"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7925"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7925"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}