题解 | #两个链表的第一个公共结点#

/* public class ListNode { int val; ListNode next = null;

ListNode(int val) {
    this.val = val;
}

}*/ import java.util.Stack; public class Solution { public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) { ListNode newNode = null; if(pHead1==null || pHead2==null) return newNode;

	Stack<ListNode> stack1 = new Stack<>();
	Stack<ListNode> stack2 = new Stack<>();
	while(pHead1.next != null) {
		stack1.push(pHead1);
		pHead1 = pHead1.next;
	}
	if(pHead1.next == null) {
		stack1.push(pHead1);
	}
	
	while(pHead2.next != null) {
		stack2.push(pHead2);
		pHead2 = pHead2.next;
	}
	if(pHead2.next == null) {
		stack2.push(pHead2);
	}
	
	boolean flag = true;//是否为第一次
	while(!stack1.empty() && !stack2.empty()) {
		if(flag) {
			if(stack1.lastElement().val == stack2.lastElement().val) {
				stack1.pop();
				stack2.pop();
				flag = false;
			}else break;
		}else {
			if(stack1.lastElement().val == stack2.lastElement().val) {
				if(stack1.size()==1 || stack2.size()==1) {
					newNode = stack1.pop();
					break;
				}
				
				stack1.pop();
				stack2.pop();
			}else{
				newNode = stack1.lastElement().next;
				break;
			}
		}
		
	}
	return newNode;
}

}