s0024

include/s0024_swap_nodes_in_pairs.hpp

@@ -0,0 +1,17 @@
+#ifndef S0024_SWAP_NODES_IN_PAIRS
+#define S0024_SWAP_NODES_IN_PAIRS
+
+struct ListNode {
+  int val;
+  ListNode* next;
+  ListNode() : val(0), next(nullptr) {}
+  ListNode(int x) : val(x), next(nullptr) {}
+  ListNode(int x, ListNode* next) : val(x), next(next) {}
+};
+
+class Solution {
+ public:
+  ListNode* swapPairs(ListNode* head);
+};
+
+#endif

src/s0024_swap_nodes_in_pairs.cpp

@@ -0,0 +1,11 @@
+#include "s0024_swap_nodes_in_pairs.hpp"
+
+ListNode* swapPairs(ListNode* head) {
+  if (head == nullptr || head->next == nullptr) {
+    return head;
+  }
+  ListNode *newHead = head->next;
+  head->next = swapPairs(newHead->next);
+  newHead->next = head;
+  return newHead;
+}