Added tasks 3-10

src/main/php/g0001_0100/s0001_two_sum/Solution.php

@@ -7,7 +7,6 @@
 // #2023_11_29_Time_9_ms_(97.47%)_Space_19.8_MB_(77.40%)
 
 class Solution {
-
     /**
      * @param Integer[] $nums
      * @param Integer $target

src/main/php/g0001_0100/s0003_longest_substring_without_repeating_characters/Solution.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace leetcode\g0001_0100\s0003_longest_substring_without_repeating_characters;
+
+// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #String #Hash_Table #Sliding_Window
+// #Algorithm_I_Day_6_Sliding_Window #Level_2_Day_14_Sliding_Window/Two_Pointer #Udemy_Strings
+// #Big_O_Time_O(n)_Space_O(1) #2023_12_03_Time_4_ms_(99.33%)_Space_19.1_MB_(68.83%)
+
+class Solution {
+    /**
+     * @param String $s
+     * @return Integer
+     */
+    public function lengthOfLongestSubstring($s) {
+        $lastIndices = array_fill(0, 256, -1);
+        $maxLen = 0;
+        $curLen = 0;
+        $start = 0;
+
+        for ($i = 0; $i < strlen($s); $i++) {
+            $cur = $s[$i];
+            $curAscii = ord($cur);
+
+            if ($lastIndices[$curAscii] < $start) {
+                $lastIndices[$curAscii] = $i;
+                $curLen++;
+            } else {
+                $lastIndex = $lastIndices[$curAscii];
+                $start = $lastIndex + 1;
+                $curLen = $i - $start + 1;
+                $lastIndices[$curAscii] = $i;
+            }
+
+            if ($curLen > $maxLen) {
+                $maxLen = $curLen;
+            }
+        }
+
+        return $maxLen;
+    }
+}

src/main/php/g0001_0100/s0003_longest_substring_without_repeating_characters/readme.md

@@ -0,0 +1,40 @@
+3\. Longest Substring Without Repeating Characters
+
+Medium
+
+Given a string `s`, find the length of the **longest substring** without repeating characters.
+
+**Example 1:**
+
+**Input:** s = "abcabcbb"
+
+**Output:** 3
+
+**Explanation:** The answer is "abc", with the length of 3. 
+
+**Example 2:**
+
+**Input:** s = "bbbbb"
+
+**Output:** 1
+
+**Explanation:** The answer is "b", with the length of 1. 
+
+**Example 3:**
+
+**Input:** s = "pwwkew"
+
+**Output:** 3
+
+**Explanation:** The answer is "wke", with the length of 3. Notice that the answer must be a substring, "pwke" is a subsequence and not a substring. 
+
+**Example 4:**
+
+**Input:** s = ""
+
+**Output:** 0 
+
+**Constraints:**
+
+*   <code>0 <= s.length <= 5 * 10<sup>4</sup></code>
+*   `s` consists of English letters, digits, symbols and spaces.

src/main/php/g0001_0100/s0004_median_of_two_sorted_arrays/Solution.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace leetcode\g0001_0100\s0004_median_of_two_sorted_arrays;
+
+// #Hard #Top_100_Liked_Questions #Top_Interview_Questions #Array #Binary_Search #Divide_and_Conquer
+// #Big_O_Time_O(log(min(N,M)))_Space_O(1) #2023_12_03_Time_23_ms_(88.34%)_Space_19.1_MB_(87.47%)
+
+class Solution {
+    /**
+     * @param Integer[] $nums1
+     * @param Integer[] $nums2
+     * @return Float
+     */
+    function findMedianSortedArrays($nums1, $nums2) {
+        $nums3 = [];
+        $sum = count($nums1) + count($nums2);
+        $med = ($sum / 2);
+        if ($sum % 2 === 0) {
+            $index = [$med - 1, $med];
+        } else {
+            $index = [floor($med)];
+        }
+        $i = 0;
+        $i1 = 0;
+        $i2 = 0;
+        while ($i < $sum) {
+            if (!isset($nums1[$i1])) {
+                $nums3[] = $nums2[$i2];
+                $i2++;
+                $i++;
+                continue;
+            }
+            if (!isset($nums2[$i2])) {
+                $nums3[] = $nums1[$i1];
+                $i1++;
+                $i++;
+                continue;
+            }
+            if ($nums1[$i1] < $nums2[$i2]) {
+                $nums3[] = $nums1[$i1];
+                $i1++;
+            } else {
+                $nums3[] = $nums2[$i2];
+                $i2++;
+            }
+            $i++;
+        }
+        return isset($index[1])
+            ? ($nums3[$index[0]] + $nums3[$index[1]]) / 2
+            : $nums3[$index[0]];
+    }
+}

src/main/php/g0001_0100/s0004_median_of_two_sorted_arrays/readme.md

@@ -0,0 +1,50 @@
+4\. Median of Two Sorted Arrays
+
+Hard
+
+Given two sorted arrays `nums1` and `nums2` of size `m` and `n` respectively, return **the median** of the two sorted arrays.
+
+The overall run time complexity should be `O(log (m+n))`.
+
+**Example 1:**
+
+**Input:** nums1 = [1,3], nums2 = [2]
+
+**Output:** 2.00000
+
+**Explanation:** merged array = [1,2,3] and median is 2. 
+
+**Example 2:**
+
+**Input:** nums1 = [1,2], nums2 = [3,4]
+
+**Output:** 2.50000
+
+**Explanation:** merged array = [1,2,3,4] and median is (2 + 3) / 2 = 2.5. 
+
+**Example 3:**
+
+**Input:** nums1 = [0,0], nums2 = [0,0]
+
+**Output:** 0.00000 
+
+**Example 4:**
+
+**Input:** nums1 = [], nums2 = [1]
+
+**Output:** 1.00000 
+
+**Example 5:**
+
+**Input:** nums1 = [2], nums2 = []
+
+**Output:** 2.00000 
+
+**Constraints:**
+
+*   `nums1.length == m`
+*   `nums2.length == n`
+*   `0 <= m <= 1000`
+*   `0 <= n <= 1000`
+*   `1 <= m + n <= 2000`
+*   <code>-10<sup>6</sup> <= nums1[i], nums2[i] <= 10<sup>6</sup></code>

src/main/php/g0001_0100/s0005_longest_palindromic_substring/Solution.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace leetcode\g0001_0100\s0005_longest_palindromic_substring;
+
+// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #String #Dynamic_Programming
+// #Data_Structure_II_Day_9_String #Algorithm_II_Day_14_Dynamic_Programming
+// #Dynamic_Programming_I_Day_17 #Udemy_Strings #Big_O_Time_O(n)_Space_O(n)
+// #2023_12_03_Time_13_ms_(98.57%)_Space_19.4_MB_(12.54%)
+
+class Solution {
+    /**
+     * @param String $s
+     * @return String
+     */
+    function longestPalindrome($s): string {
+        if (($length = strlen($s)) <= 1) {
+            return $s;
+        }
+        if (strrev($s) === $s) {
+            return $s;
+        }
+
+        $max_length = 1;
+        for ($i = 0; $i < $length; ++$i) {
+            for ($len = $max_length; $len <= $length; ++$len) {
+                $start = $i - ($len >> 1);
+                if ($start < 0 || $start + $len > $length) {
+                    break;
+                }
+                $substr = substr($s, $start, $len);
+                if ($substr === strrev($substr)) {
+                    $str = $substr;
+                    $max_length = $len;
+                } elseif ($max_length + 1 < $len) {
+                    break;
+                }
+            }
+        }
+
+        return $str;
+    }
+}

src/main/php/g0001_0100/s0005_longest_palindromic_substring/readme.md

@@ -0,0 +1,34 @@
+5\. Longest Palindromic Substring
+
+Medium
+
+Given a string `s`, return _the longest palindromic substring_ in `s`.
+
+**Example 1:**
+
+**Input:** s = "babad"
+
+**Output:** "bab" **Note:** "aba" is also a valid answer. 
+
+**Example 2:**
+
+**Input:** s = "cbbd"
+
+**Output:** "bb" 
+
+**Example 3:**
+
+**Input:** s = "a"
+
+**Output:** "a" 
+
+**Example 4:**
+
+**Input:** s = "ac"
+
+**Output:** "a" 
+
+**Constraints:**
+
+*   `1 <= s.length <= 1000`
+*   `s` consist of only digits and English letters.

src/main/php/g0001_0100/s0006_zigzag_conversion/Solution.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace leetcode\g0001_0100\s0006_zigzag_conversion;
+
+// #Medium #String #2023_12_03_Time_12_ms_(80.63%)_Space_19.3_MB_(57.66%)
+
+class Solution {
+    /**
+     * @param String $s
+     * @param Integer $numRows
+     * @return String
+     */
+    function convert($s, $numRows) {
+        if ($numRows == 1) {
+            return $s;
+        }
+        $row = 0;
+        $col = 0;
+        $dir = 'down';
+        for ($i = 0; $i < strlen($s); $i++) {
+            $string[$row][] = $s[$i];
+            if ($row < $numRows - 1 && $dir == 'down') {
+                $row++;
+            } elseif ($row == $numRows - 1 && $dir == 'down') {
+                $row--;
+                $dir = 'up';
+                $col++;
+            } elseif ($row > 0) {
+                $row--;
+                $col++;
+            } else {
+                $dir = 'down';
+                $row++;
+            }
+        }
+        return implode(array_merge(...$string));
+    }
+}

src/main/php/g0001_0100/s0006_zigzag_conversion/readme.md

@@ -0,0 +1,39 @@
+6\. Zigzag Conversion
+
+Medium
+
+The string `"PAYPALISHIRING"` is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
+
+P A H N A P L S I I G Y I R 
+
+And then read line by line: `"PAHNAPLSIIGYIR"`
+
+Write the code that will take a string and make this conversion given a number of rows:
+
+string convert(string s, int numRows); 
+
+**Example 1:**
+
+**Input:** s = "PAYPALISHIRING", numRows = 3
+
+**Output:** "PAHNAPLSIIGYIR" 
+
+**Example 2:**
+
+**Input:** s = "PAYPALISHIRING", numRows = 4
+
+**Output:** "PINALSIGYAHRPI"
+
+**Explanation:** P I N A L S I G Y A H R P I 
+
+**Example 3:**
+
+**Input:** s = "A", numRows = 1
+
+**Output:** "A" 
+
+**Constraints:**
+
+*   `1 <= s.length <= 1000`
+*   `s` consists of English letters (lower-case and upper-case), `','` and `'.'`.
+*   `1 <= numRows <= 1000`

src/main/php/g0001_0100/s0007_reverse_integer/Solution.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace leetcode\g0001_0100\s0007_reverse_integer;
+
+// #Medium #Top_Interview_Questions #Math #Udemy_Integers
+// #2023_12_03_Time_3_ms_(90.99%)_Space_19.2_MB_(44.23%)
+
+class Solution {
+    function reverse($x) {
+        $ls_negative = '';
+        if (strpos($x, '-') === 0) {
+            $ls_negative = substr($x, 0, 1);
+            $x = substr($x, 1);
+        }
+        $la_chars = str_split($x);
+        $la_chars = array_reverse($la_chars);
+        $li_result = intval($ls_negative . implode('', $la_chars));
+        if ($li_result > 2147483647 || $li_result < -2147483647) {
+            $li_result = 0;
+        }
+        return $li_result;
+    }
+}