題目描述：
輸入兩個鏈表，找出它們的第一個公共結(jié)點。
【思路】
兩個鏈表成Y字形，故只需將長的鏈表先走多余的長度，再兩個鏈表同時走，求出相應(yīng)的公共節(jié)點即可
【代碼】

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def FindFirstCommonNode(self, pHead1, pHead2):
        # write code here
        def list_len(node):
            l = 0
            while node!=None:
                l+=1
                node = node.next
            return l
        p1_len = list_len(pHead1)
        p2_len = list_len(pHead2)
        if p1_len > p2_len:
            pLong = pHead1
            pShort = pHead2
            gap_len = p1_len-p2_len
        else:
            pLong = pHead2
            pShort = pHead1
            gap_len = p2_len-p1_len
        #讓長鏈表先走
        for i in range(gap_len):
            pLong=pLong.next
        #尋找最先的公共節(jié)點
        while pLong!=None and pShort!=None:
            if pLong==pShort:
                return pLong
            else:
                pLong = pLong.next
                pShort = pShort.next