第二周作业#6

.gitignore

@@ -0,0 +1 @@
+.idea/

Week_01/id_6/LeetCode_189_6.php

@@ -0,0 +1,49 @@
+<?php
+
+
+class Solution {
+
+    /**
+     * @param Integer[] $nums
+     * @param Integer $k
+     * @return NULL
+     */
+    function rotate(&$nums, $k)
+    {
+        if ($k == 0) return;
+        $len = count($nums);
+        $k %= $len;
+
+        $this->reverse($nums, 0, $len - 1);
+        $this->reverse($nums, 0, $k - 1);
+        $this->reverse($nums, $k, $len - 1);
+
+        return;
+    }
+
+    /**
+     * revert an array
+     *
+     * @param $nums
+     * @param $start
+     * @param $end
+     */
+    private function reverse(&$nums, $start, $end)
+    {
+        while ($start < $end) {
+            $tmp = $nums[$start];
+            $nums[$start] = $nums[$end];
+            $nums[$end] = $tmp;
+
+            $start ++;
+            $end --;
+        }
+
+        return;
+    }
+}
+
+$nums = [1,2,3,4,5,6,7];
+$sol = new Solution();
+$sol->rotate2($nums, 3);
+var_export($nums);

Week_01/id_6/LeetCode_21_6.php

@@ -0,0 +1,54 @@
+<?php
+
+
+/**
+ * Definition for a singly-linked list.
+ * class ListNode {
+ *     public $val = 0;
+ *     public $next = null;
+ *     function __construct($val) { $this->val = $val; }
+ * }
+ */
+class Solution {
+
+    /**
+     * @param ListNode $l1
+     * @param ListNode $l2
+     * @return ListNode
+     */
+    function mergeTwoLists($l1, $l2)
+    {
+        if (null == $l1) return $l2;
+        if (null == $l2) return $l1;
+
+        $list = new ListNode(0);
+        $cur = $list;
+        while (null != $l1 && null != $l2) {
+            if ($l1->val < $l2->val) {
+                $cur->next = $l1;
+                $cur = $cur->next;
+                $l1 = $l1->next;
+            } else {
+                $cur->next = $l2;
+                $cur = $cur->next;
+                $l2 = $l2->next;
+            }
+        }
+
+        if ($l1 == null) {
+            $cur->next = $l2;
+        }
+
+        if ($l2 == null) {
+            $cur->next = $l1;
+        }
+
+        return $list->next;
+    }
+}
+
+class ListNode {
+    public $val = 0;
+    public $next = null;
+    function __construct($val) { $this->val = $val; }
+}

Week_01/id_6/LeetCode_26_6.php

@@ -0,0 +1,29 @@
+<?php
+
+
+class Solution {
+
+    /**
+     * @param Integer[] $nums
+     * @return Integer
+     */
+    function removeDuplicates(&$nums)
+    {
+        $flag = 1;
+        $num = $nums[0];
+        for ($i = 1; $i < count($nums); $i ++) {
+            if ($nums[$i] == $num) {
+                unset($nums[$i]);
+            } else {
+                $num = $nums[$i];
+                $flag++;
+            }
+        }
+
+        return $flag;
+    }
+}
+
+$nums = [0,0,1,1,1,2,2,3,3,4];
+$sol = new Solution();
+echo $sol->removeDuplicates($nums);

Week_01/id_6/LeetCode_88_6.php

@@ -0,0 +1,51 @@
+<?php
+
+class Solution
+{
+
+    /**
+     * @param Integer[] $nums1
+     * @param Integer $m
+     * @param Integer[] $nums2
+     * @param Integer $n
+     * @return NULL
+     */
+    function merge(&$nums1, $m, $nums2, $n)
+    {
+        $len = $m + $n;
+        while ($m > 0 && $n > 0) {
+            if ($nums1[$m - 1] > $nums2[$n - 1]) {
+                $nums1[$len - 1] = $nums1[$m - 1];
+                $m --;
+            } else {
+                $nums1[$len - 1] = $nums2[$n - 1];
+                $n --;
+            }
+            $len --;
+        }
+
+        while ($n > 0) {
+            $nums1[$len - 1] = $nums2[$n - 1];
+            $n --;
+            $len --;
+        }
+
+        return;
+    }
+}
+
+$nums1 = [2,0];
+$m = 1;
+
+$nums2 = [1];
+$n = 1;
+/*
+$nums1 = [1,2,3,0,0,0];
+$m = 3;
+
+$nums2 = [2,5,6];
+$n = 3;*/
+
+$sol = new Solution();
+$sol->merge($nums1, $m, $nums2, $n);
+var_export($nums1);

Week_01/id_6/NOTE.md

@@ -1 +1,7 @@
 # 学习笔记
+
+主要练习了数组和链表的习题，每道题都会根据所学思考不同的算法解法。数组和链表树所有数据结构和算法的基础，用数组和链表去实现其他的数据结构，如堆、栈、树等等，手写一遍代码 ，会更加加深自己对于其中数据结构和算法的掌握。
+
+在平时的工作之中，自己会刻意地去想有没有更好、更优化的解决方案，这个业务的时间复杂度是多少、空间复杂度是多少，有没有更加优化的解决方案，可以减少内存占用或者服务器资源占用，自己会更多地去思考这方面的问题，这对于自己的平时工作也是一个很的提升。
+
+本周联系的题目不算多，但是自己对于每一个题目的思考有很多，不只是每道题目的解法算法，还有不同的思路，自己选择的算法与数据结构，开拓了自己从前没有思考过的思维，并且能够把这种思维应用到实际的业务和场景中，这是自己最大的收获。

Week_02/id_6/LeetCode_101_6.php

@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     public $val = null;
+ *     public $left = null;
+ *     public $right = null;
+ *     function __construct($value) { $this->val = $value; }
+ * }
+ */
+class Solution {
+
+    /**
+     * @param TreeNode $root
+     * @return Boolean
+     */
+    function isSymmetric($root)
+    {
+        $this->isSymmetricRec($root, $root);
+    }
+
+    /**
+     * @param TreeNode $left_root
+     * @param TreeNode $right_root
+     * @return Boolean
+     */
+    function isSymmetricRec($left_root, $right_root)
+    {
+        if ($left_root == null && $right_root == null) return true;
+        if ($left_root == null || $right_root == null) return false;
+        if ($left_root->val == $right_root->val) {
+            return $this->isSymmetricRec($left_root->left, $right_root->right) && $this->isSymmetricRec($left_root->right, $right_root->left);
+        }
+        return false;
+    }
+}

Week_02/id_6/LeetCode_102_6.php

@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     public $val = null;
+ *     public $left = null;
+ *     public $right = null;
+ *     function __construct($value) { $this->val = $value; }
+ * }
+ */
+class Solution {
+
+    public $levels = [];
+
+    /**
+     * @param TreeNode $root
+     * @return Integer[][]
+     */
+    function levelOrder($root)
+    {
+        if ($root == null) return [];
+        // BFS
+        $this->bfs($root, 0);
+        return $this->levels;
+
+    }
+
+    function bfs($root, $level)
+    {
+        $this->levels[$level][] = $root->val;
+
+        if ($root->left != null) {
+            $this->bfs($root->left, $level + 1);
+        }
+
+        if ($root->right != null) {
+            $this->bfs($root->right, $level + 1);
+        }
+    }
+}

Week_02/id_6/LeetCode_103_6.php

@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     public $val = null;
+ *     public $left = null;
+ *     public $right = null;
+ *     function __construct($value) { $this->val = $value; }
+ * }
+ */
+class Solution {
+
+    public $levels = [];
+
+    /**
+     * @param TreeNode $root
+     * @return Integer[][]
+     */
+    function zigzagLevelOrder($root) {
+        if ($root == null) return [];
+        // BFS
+        $this->bfs($root, 0);
+        return $this->levels;
+    }
+
+    function bfs($root, $level)
+    {
+        if ($level % 2 != 0) {
+            if (!isset($this->levels[$level])) $this->levels[$level] = [];
+            array_unshift($this->levels[$level], $root->val);
+        } else {
+            $this->levels[$level][] = $root->val;
+        }
+
+        if ($root->left != null) {
+            $this->bfs($root->left, $level + 1);
+        }
+
+        if ($root->right != null) {
+            $this->bfs($root->right, $level + 1);
+        }
+    }
+}

Week_02/id_6/LeetCode_3_6.php

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+<?php
+
+class Solution {
+
+    /**
+     * @param String $s
+     * @return Integer
+     */
+    function lengthOfLongestSubstring($s) {
+        $hash = [];
+        $len = strlen($s);
+        $count = $i = $j = 0;
+        while ($i < $len && $j < $len) {
+            if (!isset($hash[$s[$j]])) {
+                $hash[$s[$j]] = 1;
+                $j ++;
+                $count = max($count, $j - $i);
+            } else {
+                unset($hash[$s[$i]]);
+                $i ++;
+            }
+        }
+
+        return $count;
+    }
+}
+
+$sol = new Solution();
+$s = "abcabcbb";
+var_dump($sol->lengthOfLongestSubstring($s));

Week_02/id_6/LeetCode_938_6.php

@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     public $val = null;
+ *     public $left = null;
+ *     public $right = null;
+ *     function __construct($value) { $this->val = $value; }
+ * }
+ */
+class Solution {
+
+    /**
+     * @param TreeNode $root
+     * @param Integer $L
+     * @param Integer $R
+     * @return Integer
+     */
+    function rangeSumBST($root, $L, $R)
+    {
+        if ($root == null) return $this->sum;
+        if ($root->val > $R) {
+            return $this->rangeSumBST($root->left, $L, $R);
+        }
+        if ($root->val < $L) {
+            return $this->rangeSumBST($root->right, $L, $R);
+        }
+        return $root->val + $this->rangeSumBST($root->left, $L, $R) + $this->rangeSumBST($root->right, $L, $R);
+    }
+
+}