题解 | #链表中环的入口结点#

/**

• struct ListNode {
• int val;
• struct ListNode *next;
• };
• C语言声明定义全局变量请加上static，防止重复定义 / /*
• 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
• @param pHead ListNode类
• @return ListNode类 / #include <stdbool.h> bool hasCycle(struct ListNode head ) { // write code here if(head == NULL) return false; struct ListNode p = head; for(int i = 1;i<10000;i++) { p = p->next; if(p == NULL) return false; } return true; } struct ListNode EntryNodeOfLoop(struct ListNode* pHead ) { // write code here if(hasCycle(pHead) == false) return NULL; struct ListNode *p1,*p2; p1 = pHead; int count = 0; for(int i = 1;i<= 10000;i++) p1 = p1->next; p2 = p1; do { count++; p1 = p1->next; }while(p1 != p2); p2 = p1 = pHead; do { p2 = p1; for( int i = 1;i<=count;i++) { p2 = p2->next;
  } if(p2 == p1) return p2; else p1 = p1->next; }while(1);

}