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diff --git a/Regex/Applications/1-detect-html-links.js b/Regex/Applications/1-detect-html-links.js
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index 0000000..91fe545
--- /dev/null
+++ b/Regex/Applications/1-detect-html-links.js
@@ -0,0 +1,8 @@
+function processData(input) {
+    var regex=/<a.*?href="(.*?)".*?>(.*?)<\/a>/ig;
+    var output=[];
+    input.replace(regex,function(_,href,text){
+        output.push(href.trim()+','+text.replace(/<.*?>/g,'').trim())
+    });
+    console.log(output.join('\n'));
+}
diff --git a/Regex/Applications/1-detect-html-links.php b/Regex/Applications/1-detect-html-links.php
new file mode 100644
index 0000000..868d0e4
--- /dev/null
+++ b/Regex/Applications/1-detect-html-links.php
@@ -0,0 +1,15 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$html = '';
+while ($t --) {
+    $html .= trim(fgets($handle));
+}
+
+if (preg_match_all('/<a .*?href="(.*?)".*?>(.*?)<\/a>/', $html, $matches)) {
+    foreach ($matches[1] as $i => $link) {
+        printf("%s,%s\n", $link, trim(strip_tags($matches[2][$i])));
+    }
+}
diff --git a/Regex/Applications/10-detecting-valid-latitude-and-longitude.php b/Regex/Applications/10-detecting-valid-latitude-and-longitude.php
new file mode 100644
index 0000000..fc7c02b
--- /dev/null
+++ b/Regex/Applications/10-detecting-valid-latitude-and-longitude.php
@@ -0,0 +1,21 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$lines = [];
+while ($t --) {
+    $lines[] = trim(fgets($handle));
+}
+
+foreach ($lines as $line) {
+    if (preg_match_all('/\(\+?-?((?:[1-9]\d*)|(?:[1-9]\d*)\.\d+), \+?-?((?:[1-9]\d*)|(?:[1-9]\d*)\.\d+)\)/', $line, $matches)) {
+        if ($matches[1][0] > 90 || $matches[2][0] > 180) {
+            echo "Invalid\n";
+        } else {
+            echo "Valid\n";
+        }
+    } else {
+        echo "Invalid\n";
+    }
+}
diff --git a/Regex/Applications/11-hackerrank-tweets.php b/Regex/Applications/11-hackerrank-tweets.php
new file mode 100644
index 0000000..568e91f
--- /dev/null
+++ b/Regex/Applications/11-hackerrank-tweets.php
@@ -0,0 +1,11 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$twitters = '';
+while ($t --) {
+    $twitters .= trim(fgets($handle)) . " ";
+}
+
+echo preg_match_all('/HackerRank/i', $twitters);
diff --git a/Regex/Applications/12-stack-exchange-scraper.php b/Regex/Applications/12-stack-exchange-scraper.php
new file mode 100644
index 0000000..cb4d922
--- /dev/null
+++ b/Regex/Applications/12-stack-exchange-scraper.php
@@ -0,0 +1,15 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+
+$html = '';
+$t = 3600;
+while ($t --) {
+    $html .= trim(fgets($handle)) . "\n";
+}
+
+preg_match_all('/(?:<h3><a href="\/questions\/(\d*).*>(.*)<\/a>|class="relativetime">(.*)<\/span>)/', $html, $matches);
+
+for ($i = 0; $i < count($matches[0]) / 2; $i ++) {
+    printf("%s;%s;%s\n", $matches[1][$i * 2], $matches[2][$i * 2], $matches[3][($i + 1) * 2 - 1]);
+}
diff --git a/Regex/Applications/13-utopian-identification-number.php b/Regex/Applications/13-utopian-identification-number.php
new file mode 100644
index 0000000..57ba9c3
--- /dev/null
+++ b/Regex/Applications/13-utopian-identification-number.php
@@ -0,0 +1,11 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$regex = '/^[a-z]{0,3}\d{2,8}[A-Z]{3,}$/';
+while ($t --) {
+    fscanf($handle, "%s", $s);
+
+    echo preg_match($regex, $s) ? "VALID\n" : "INVALID\n";
+}
diff --git a/Regex/Applications/14-valid-pan-format.php b/Regex/Applications/14-valid-pan-format.php
new file mode 100644
index 0000000..3b243cc
--- /dev/null
+++ b/Regex/Applications/14-valid-pan-format.php
@@ -0,0 +1,11 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$regex = '/^[A-Z]{5}[0-9]{4}[A-Z]$/';
+while ($t --) {
+    fscanf($handle, "%s", $s);
+
+    echo preg_match($regex, $s) ? "VALID\n" : "INVALID\n";
+}
diff --git a/Regex/Applications/15-find-hackerrank.php b/Regex/Applications/15-find-hackerrank.php
new file mode 100644
index 0000000..6b084e8
--- /dev/null
+++ b/Regex/Applications/15-find-hackerrank.php
@@ -0,0 +1,23 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+while ($t --) {
+    $s = trim(fgets($handle));
+
+    if ($s == 'hackerrank') {
+        echo "0\n";
+    } else {
+        $pos = strpos($s, 'hackerrank');
+        if ($pos === false) {
+            echo "-1\n";
+        } else if ($pos === 0) {
+            echo "1\n";
+        } else if ($pos + 10 == strlen($s)) {
+            echo "2\n";
+        } else {
+            echo "-1\n";
+        }
+    }
+}
diff --git a/Regex/Applications/16-saying-hi.php b/Regex/Applications/16-saying-hi.php
new file mode 100644
index 0000000..6abea4a
--- /dev/null
+++ b/Regex/Applications/16-saying-hi.php
@@ -0,0 +1,20 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+$languages = ['C','CPP','JAVA','PYTHON','PERL','PHP','RUBY','CSHARP','HASKELL','CLOJURE','BASH','SCALA','ERLANG','CLISP','LUA','BRAINFUCK','JAVASCRIPT','GO','D','OCAML','R','PASCAL','SBCL','DART','GROOVY','OBJECTIVEC'];
+
+while ($t --) {
+    $s = trim(fgets($handle));
+
+    if (preg_match('/(\d{1,5}) ([A-Z]+)/', $s, $matches)) {
+        print_r($matches);
+        if ($matches[1] >= 10000 && $matches[1] < 100000 && in_array($matches[2], $languages)) {
+            echo "VALID\n";
+        } else {
+            echo "INVALID\n";
+        }
+    } else {
+        echo "INVALID\n";
+    }
+}
diff --git a/Regex/Applications/17-programming-language-detection.php b/Regex/Applications/17-programming-language-detection.php
new file mode 100644
index 0000000..57746dc
--- /dev/null
+++ b/Regex/Applications/17-programming-language-detection.php
@@ -0,0 +1,20 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+
+$code = '';
+$t = 1000;
+while ($t --) {
+    $code .= trim(fgets($handle)) . "\n";
+}
+
+$regex_c = '/#include/';
+$regex_java = '/import java/';
+
+if (preg_match($regex_c, $code)) {
+    echo "C\n";
+}  else if (preg_match($regex_java, $code)) {
+    echo "Java\n";
+} else {
+    echo "Python\n";
+}
diff --git a/Regex/Applications/18-split-number.php b/Regex/Applications/18-split-number.php
new file mode 100644
index 0000000..478058f
--- /dev/null
+++ b/Regex/Applications/18-split-number.php
@@ -0,0 +1,13 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+$regex = '/^(\d{1,3})(\?|(?: )|(?:-))(\d{1,3})\2(\d{4,10})$/';
+
+while ($t --) {
+    $string = trim(fgets($handle));
+
+    if (preg_match($regex, $string, $matches)) {
+        printf("CountryCode=%s,LocalAreaCode=%s,Number=%s\n", $matches[1], $matches[3], $matches[4]);
+    }
+}
diff --git a/Regex/Applications/19-html-attributes.php b/Regex/Applications/19-html-attributes.php
new file mode 100644
index 0000000..b879d82
--- /dev/null
+++ b/Regex/Applications/19-html-attributes.php
@@ -0,0 +1,13 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+$regex = '//';
+
+while ($t --) {
+    $string = trim(fgets($handle));
+
+    if (preg_match($regex, $string, $matches)) {
+        printf("CountryCode=%s,LocalAreaCode=%s,Number=%s\n", $matches[1], $matches[3], $matches[4]);
+    }
+}
diff --git a/Regex/Applications/2-detect-html-tags.php b/Regex/Applications/2-detect-html-tags.php
new file mode 100644
index 0000000..5949395
--- /dev/null
+++ b/Regex/Applications/2-detect-html-tags.php
@@ -0,0 +1,23 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$html = '';
+while ($t --) {
+    $html .= trim(fgets($handle));
+}
+
+$tags = [];
+$regex = '/(<\s*([\w]+) ?.*?>|\[.*?\])/';
+
+if (preg_match_all($regex, $html, $matches)) {
+    foreach ($matches[2] as $g) {
+        $tags[] = $g ?: 'a';
+    }
+}
+
+$tags = array_unique($tags);
+sort($tags);
+
+echo implode(";", $tags) . PHP_EOL;
diff --git a/Regex/Applications/20-html-attributes.php b/Regex/Applications/20-html-attributes.php
new file mode 100644
index 0000000..c68d80b
--- /dev/null
+++ b/Regex/Applications/20-html-attributes.php
@@ -0,0 +1,46 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+$regex_1 = '/<([a-zA-Z0-9]+) ?(?:\w*="?\'?[^"\']*\'?"? ?){0,}/';
+$regex_2 = '/ (\w*)=/';
+
+$code = [];
+
+while ($t --) {
+    $code[] = trim(fgets($handle));
+}
+
+$tags = [];
+
+foreach ($code as $c) {
+    if (preg_match_all($regex_1, $c, $matches_1)) {
+        for ($i = 0; $i < count($matches_1[0]); $i ++) {
+            if (strpos($matches_1[0][$i], '=') !== false) {
+                preg_match_all($regex_2, $matches_1[0][$i], $matches_2);
+
+                foreach ($matches_2[1] as $attr) {
+                    if (! isset($tags[$matches_1[1][$i]])) {
+                        $tags[$matches_1[1][$i]][] = $attr;
+                    } else {
+                        if (! in_array($attr, $tags[$matches_1[1][$i]])) {
+                            $tags[$matches_1[1][$i]][] = $attr;
+                        }
+                    }
+                }
+            } else {
+                if (! isset($tags[$matches_1[1][$i]])) {
+                    $tags[$matches_1[1][$i]] = [];
+                }
+            }
+        }
+    }
+}
+
+ksort($tags);
+
+foreach ($tags as $tag => $attributes) {
+    sort($attributes);
+
+    printf("%s:%s\n", $tag, implode(',', $attributes));
+}
diff --git a/Regex/Applications/21-uk-and-us.php b/Regex/Applications/21-uk-and-us.php
new file mode 100644
index 0000000..a310f5a
--- /dev/null
+++ b/Regex/Applications/21-uk-and-us.php
@@ -0,0 +1,18 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$words = '';
+while ($t --) {
+    $words .= trim(fgets($handle)) . " ";
+}
+
+fscanf($handle, "%d", $n);
+
+while ($n --) {
+    fscanf($handle, "%s", $s);
+    $regex = '/' . substr($s, 0, strlen($s) - 2) . '[sz]' . substr($s, strlen($s) - 1) . '/';
+
+    printf("%d\n", preg_match_all($regex, $words));
+}
diff --git a/Regex/Applications/22-uk-and-us-2.php b/Regex/Applications/22-uk-and-us-2.php
new file mode 100644
index 0000000..dc378e6
--- /dev/null
+++ b/Regex/Applications/22-uk-and-us-2.php
@@ -0,0 +1,23 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$words = '';
+while ($t --) {
+    $words .= trim(fgets($handle)) . " ";
+}
+
+fscanf($handle, "%d", $n);
+
+while ($n --) {
+    fscanf($handle, "%s", $s);
+    $s = str_replace("our", "ou?r", $s);
+    $regex = '/(?=\b' . $s . '\b)/i';
+
+    if (preg_match_all($regex, $words, $matches)) {
+        echo count($matches[0]) . "\n";
+    } else {
+        echo "0\n";
+    }
+}
diff --git a/Regex/Applications/3-find-substring.php b/Regex/Applications/3-find-substring.php
new file mode 100644
index 0000000..33700c9
--- /dev/null
+++ b/Regex/Applications/3-find-substring.php
@@ -0,0 +1,25 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+while ($t --) {
+    $lines[] = trim(fgets($handle));
+}
+
+fscanf($handle, "%d", $n);
+
+while ($n --) {
+    $count = 0;
+    fscanf($handle, "%s", $pattern);
+    $regex = "/[0-9a-zA-Z_]+" . $pattern . "[0-9a-zA-Z_]+/";
+    foreach ($lines as $line) {
+        foreach (explode(" ", $line) as $word) {
+            if (preg_match($regex, $word)) {
+                $count ++;
+            }
+        }
+    }
+
+    echo $count . PHP_EOL;
+}
diff --git a/Regex/Applications/4-alien-username.php b/Regex/Applications/4-alien-username.php
new file mode 100644
index 0000000..43d2a42
--- /dev/null
+++ b/Regex/Applications/4-alien-username.php
@@ -0,0 +1,12 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+while ($t --) {
+    fscanf($handle, "%s", $username);
+
+    $regex = '/^[\._]\d+[a-zA-Z]*_?$/';
+
+    echo preg_match($regex, $username) ? "VALID\n" : "INVALID\n";
+}
diff --git a/Regex/Applications/5-ip-address-validation.php b/Regex/Applications/5-ip-address-validation.php
new file mode 100644
index 0000000..acc0d0f
--- /dev/null
+++ b/Regex/Applications/5-ip-address-validation.php
@@ -0,0 +1,19 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$ip4_regex = '/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/';
+$ip6_regex = '/^(?:[a-fA-F0-9]{1,4}:){7}[a-fA-F0-9]{1,4}$/';
+
+while ($t --) {
+    fscanf($handle, "%s", $str);
+
+    if (preg_match($ip4_regex, $str)) {
+        printf("IPv4\n");
+    } else if (preg_match($ip6_regex, $str)) {
+        printf("IPv6\n");
+    } else {
+        printf("Neither\n");
+    }
+}
diff --git a/Regex/Applications/6-find-a-word.php b/Regex/Applications/6-find-a-word.php
new file mode 100644
index 0000000..5b525a6
--- /dev/null
+++ b/Regex/Applications/6-find-a-word.php
@@ -0,0 +1,20 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$lines = '';
+while ($t --) {
+    $lines .= ' ' . trim(fgets($handle));
+}
+
+fscanf($handle, "%d", $n);
+
+while ($n --) {
+    fscanf($handle, "%s", $word);
+    $count = 0;
+
+    $regex = '/(\b' . $word. '\b)/';
+
+    printf("%d\n", preg_match_all($regex, $lines));
+}
diff --git a/Regex/Applications/7-detect-the-email-addresses.php b/Regex/Applications/7-detect-the-email-addresses.php
new file mode 100755
index 0000000..91988ff
--- /dev/null
+++ b/Regex/Applications/7-detect-the-email-addresses.php
@@ -0,0 +1,18 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+fscanf($handle, "%d", $t);
+
+$lines = '';
+while ($t --) {
+    $lines .= ' ' . trim(fgets($handle));
+}
+
+fscanf($handle, "%d", $n);
+
+preg_match_all('/\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.*\b/', $lines, $emails);
+
+$emails = array_unique($emails[0]);
+sort($emails);
+
+printf("%s\n", implode(";", $emails));
diff --git a/Regex/Applications/8-detect-the-domain-name.php b/Regex/Applications/8-detect-the-domain-name.php
new file mode 100644
index 0000000..ea37c37
--- /dev/null
+++ b/Regex/Applications/8-detect-the-domain-name.php
@@ -0,0 +1,19 @@
+<?php
+
+$fp = fopen("php://stdin", "r");
+$n = fgets($fp);
+$s = "";
+for(;$n>0;$n-=1)
+    $s.=fgets($fp);
+
+$s = preg_replace("/(ww[w2-9]\.)/", "", $s);
+preg_match_all("/https?:\/\/([a-z0-9._\-]+)/", $s, $m);
+
+foreach($m[1] as $v) {
+  if(!preg_match("/[a-z0-9_\-]+\.[a-z]+$/", $v))
+    continue;
+  $arr[] = $v;
+}
+$arr = array_unique($arr);
+sort($arr);
+echo implode(";", $arr);
diff --git a/Regex/Applications/9-ide-identifying-comments.php b/Regex/Applications/9-ide-identifying-comments.php
new file mode 100644
index 0000000..30841f3
--- /dev/null
+++ b/Regex/Applications/9-ide-identifying-comments.php
@@ -0,0 +1,13 @@
+<?php
+
+$handle = fopen("php://stdin", "r");
+$code = '';
+
+$i = 200;
+while ($i --) {
+    $code .= trim(fgets($handle)) . "\n";
+}
+
+if (preg_match_all('/(\/\*(\s|.)*?\*\/|\/\/[^\n]*)/', $code, $matches)) {
+    echo implode("\n", $matches[1]);
+}
diff --git a/Regex/Assertions/1-Positive-lookahead.php b/Regex/Assertions/1-Positive-lookahead.php
new file mode 100644
index 0000000..3d068f6
--- /dev/null
+++ b/Regex/Assertions/1-Positive-lookahead.php
@@ -0,0 +1,3 @@
+<?php
+
+$Regex_Pattern = '/o(?=oo)/';
diff --git a/Regex/Assertions/2-negative-lookahead.php b/Regex/Assertions/2-negative-lookahead.php
new file mode 100644
index 0000000..1228091
--- /dev/null
+++ b/Regex/Assertions/2-negative-lookahead.php
@@ -0,0 +1,3 @@
+<?php
+
+$Regex_Pattern = '/(.)(?!\1)/';
diff --git a/Regex/Assertions/3-positive-lookbehind.php b/Regex/Assertions/3-positive-lookbehind.php
new file mode 100644
index 0000000..5c69a18
--- /dev/null
+++ b/Regex/Assertions/3-positive-lookbehind.php
@@ -0,0 +1,3 @@
+<?php
+
+$Regex_Pattern = '/(?<=[13579])[0-9]/';
diff --git a/Regex/Assertions/4-negative-lookbehind.php b/Regex/Assertions/4-negative-lookbehind.php
new file mode 100644
index 0000000..7a6d76b
--- /dev/null
+++ b/Regex/Assertions/4-negative-lookbehind.php
@@ -0,0 +1,3 @@
+<?php
+
+$Regex_Pattern = '/(?<![aeiouAEIOU])./';
diff --git a/Regex/Backreferences/1-matching-same-text-again-again.php b/Regex/Backreferences/1-matching-same-text-again-again.php
old mode 100644
new mode 100755
diff --git a/Regex/Backreferences/2-backreferences-to-failed-groups.php b/Regex/Backreferences/2-backreferences-to-failed-groups.php
old mode 100644
new mode 100755
diff --git a/Regex/Backreferences/3-branch-reset-groups.php b/Regex/Backreferences/3-branch-reset-groups.php
old mode 100644
new mode 100755
diff --git a/Regex/Backreferences/4-forward-references.php b/Regex/Backreferences/4-forward-references.php
new file mode 100644
index 0000000..1e34854
--- /dev/null
+++ b/Regex/Backreferences/4-forward-references.php
@@ -0,0 +1,3 @@
+<?php
+
+$Regex_Pattern = '^(\2tic|(tac))+$';
diff --git a/Regex/Character Class/1-matching-specific-characters.php b/Regex/Character Class/1-matching-specific-characters.php
old mode 100644
new mode 100755
diff --git a/Regex/Character Class/2-excluding-specific-characters.php b/Regex/Character Class/2-excluding-specific-characters.php
old mode 100644
new mode 100755
diff --git a/Regex/Character Class/3-matching-range-of-characters.php b/Regex/Character Class/3-matching-range-of-characters.php
old mode 100644
new mode 100755
diff --git a/Regex/Grouping and Capturing/1-matching-word-boundaries.php b/Regex/Grouping and Capturing/1-matching-word-boundaries.php
old mode 100644
new mode 100755
diff --git a/Regex/Grouping and Capturing/2-capturing-non-capturing-groups.php b/Regex/Grouping and Capturing/2-capturing-non-capturing-groups.php
old mode 100644
new mode 100755
diff --git a/Regex/Grouping and Capturing/3-alternative-matching.php b/Regex/Grouping and Capturing/3-alternative-matching.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/1-matching-specific-string.php b/Regex/Introduction/1-matching-specific-string.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/2-matching-anything-but-new-line.php b/Regex/Introduction/2-matching-anything-but-new-line.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/3-matching-digits-non-digit-character.php b/Regex/Introduction/3-matching-digits-non-digit-character.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/4-matching-whitespace-non-whitespace-character.php b/Regex/Introduction/4-matching-whitespace-non-whitespace-character.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/5-matching-word-non-word.php b/Regex/Introduction/5-matching-word-non-word.php
old mode 100644
new mode 100755
diff --git a/Regex/Introduction/6-matching-start-end.php b/Regex/Introduction/6-matching-start-end.php
old mode 100644
new mode 100755
diff --git a/Regex/Repetitions/1-matching-x-repetitions.php b/Regex/Repetitions/1-matching-x-repetitions.php
old mode 100644
new mode 100755
diff --git a/Regex/Repetitions/2-matching-x-y-repititions.php b/Regex/Repetitions/2-matching-x-y-repititions.php
old mode 100644
new mode 100755
diff --git a/Regex/Repetitions/3-matching-zero-or-more-repetitions.php b/Regex/Repetitions/3-matching-zero-or-more-repetitions.php
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