feat: add cpp solutions to lcof problems No.21,22,24

Author: maolonglong

lcof/面试题21. 调整数组顺序使奇数位于偶数前面/README.md

@@ -93,6 +93,27 @@ var exchange = function (nums) {
 };
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    vector<int> exchange(vector<int>& nums) {
+        int left = 0, right = nums.size() - 1;
+        while (left < right) {
+            while (left < right && (nums[left] & 1) == 1) {
+                ++left;
+            }
+            while (left < right && (nums[right] & 1) == 0) {
+                --right;
+            }
+            swap(nums[left], nums[right]);
+        }
+        return nums;
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题21. 调整数组顺序使奇数位于偶数前面/Solution.cpp

@@ -0,0 +1,16 @@
+class Solution {
+public:
+    vector<int> exchange(vector<int>& nums) {
+        int left = 0, right = nums.size() - 1;
+        while (left < right) {
+            while (left < right && (nums[left] & 1) == 1) {
+                ++left;
+            }
+            while (left < right && (nums[right] & 1) == 0) {
+                --right;
+            }
+            swap(nums[left], nums[right]);
+        }
+        return nums;
+    }
+};

lcof/面试题22. 链表中倒数第k个节点/README.md

@@ -118,6 +118,25 @@ func getKthFromEnd(head *ListNode, k int) *ListNode {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    ListNode* getKthFromEnd(ListNode* head, int k) {
+        ListNode *slow = head, *fast = head;
+        while (k--) {
+            fast = fast->next;
+        }
+        while (fast) {
+            slow = slow->next;
+            fast = fast->next;
+        }
+        return slow;
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题22. 链表中倒数第k个节点/Solution.cpp

@@ -0,0 +1,14 @@
+class Solution {
+public:
+    ListNode* getKthFromEnd(ListNode* head, int k) {
+        ListNode *slow = head, *fast = head;
+        while (k--) {
+            fast = fast->next;
+        }
+        while (fast) {
+            slow = slow->next;
+            fast = fast->next;
+        }
+        return slow;
+    }
+};

lcof/面试题24. 反转链表/README.md

@@ -116,6 +116,36 @@ func reverseList(head *ListNode) *ListNode {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    ListNode* reverseList(ListNode* head) {
+        // 通过头插实现逆序
+        // ListNode *first = new ListNode(-1);
+        // ListNode *p = head, *q;
+        // while (p) {
+        //     q = p->next;
+        //     p->next = first->next;
+        //     first->next = p;
+        //     p = q;
+        // }
+        // return first->next;
+
+        // 常规方法
+        ListNode *pre = NULL, *cur = head;
+        while (cur) {
+            ListNode* temp = cur->next;
+            cur->next = pre;
+            pre = cur;
+            cur = temp;
+        }
+        return pre;
+    }
+};
+```
+
 ### **...**
 
 ```

lcof/面试题24. 反转链表/Solution.cpp

@@ -0,0 +1,25 @@
+class Solution {
+public:
+    ListNode* reverseList(ListNode* head) {
+        // 通过头插实现逆序
+        // ListNode *first = new ListNode(-1);
+        // ListNode *p = head, *q;
+        // while (p) {
+        //     q = p->next;
+        //     p->next = first->next;
+        //     first->next = p;
+        //     p = q;
+        // }
+        // return first->next;
+
+        // 常规方法
+        ListNode *pre = NULL, *cur = head;
+        while (cur) {
+            ListNode* temp = cur->next;
+            cur->next = pre;
+            pre = cur;
+            cur = temp;
+        }
+        return pre;
+    }
+};