s0160

include/s0160_intersection_of_two_linked_lists.hpp

@@ -0,0 +1,15 @@
+#ifndef S0160_INTERSECTION_OF_TWO_LINKED_LISTS_HPP
+#define S0160_INTERSECTION_OF_TWO_LINKED_LISTS_HPP
+
+struct ListNode {
+  int val;
+  ListNode *next;
+  ListNode(int x) : val(x), next(nullptr) {}
+};
+
+class S0160 {
+ public:
+  ListNode *getIntersectionNode(ListNode *headA, ListNode *headB);
+};
+
+#endif

notes/src/linked-list.md

@@ -1 +1,22 @@
 # 总结
+
+首先考虑递归 (e.g. s0206, s0024)
+
+其次考虑双指针 (e.g. s0206, s0019, s0160)
+
+递归遍历单链表：
+
+```cpp
+void iter(ListNode *node) {
+  if (node == nullptr) {
+    return;
+  }
+  /*
+   your
+   condition
+   */
+  iter(node->next);
+}
+```
+
+递归遍历的意义在于让回溯单链表，也就是先遍历到结尾，然后从后往前遍历到某个 condition 。

src/s0160_intersection_of_two_linked_lists.cpp

@@ -0,0 +1,33 @@
+#include "s0160_intersection_of_two_linked_lists.hpp"
+
+ListNode *S0160::getIntersectionNode(ListNode *headA, ListNode *headB) {
+  // 获取两个链表的长度
+  int lenA{0};
+  for (ListNode *ptr = headA; ptr != nullptr; ptr = ptr->next) {
+    ++lenA;
+  }
+  int lenB{0};
+  for (ListNode *ptr = headB; ptr != nullptr; ptr = ptr->next) {
+    ++lenB;
+  }
+  // 设置两个指针的起始位置
+  ListNode *ptrA = headA, *ptrB = headB;
+  if (lenA > lenB) {
+    for (int i{0}; i < lenA - lenB; ++i) {
+      ptrA = ptrA->next;
+    }
+  } else if (lenA < lenB) {
+    for (int i{0}; i < lenB - lenA; ++i) {
+      ptrB = ptrB->next;
+    }
+  }
+  // 两个指针开始同时往前
+  while (ptrA != nullptr) {
+    if (ptrA == ptrB) {
+      return ptrA;
+    }
+    ptrA = ptrA->next;
+    ptrB = ptrB->next;
+  }
+  return nullptr;
+}