02.07. 链表相交

02.07. 链表相交

ListNode* curA=headA;
ListNode* curB=headB;
int lenA=0,lenB=0;
while(curA!=NULL){
    lenA++;//A长度
    curA=curA->next;
}
while(curB!=NULL){
    lenB++;//B长度
    curB=curB->next;
}
curA=headA;
curB=headB;
//curA become max ,lenA is its length
if(lenB>lenA){
    swap(lenA,lenB);
    swap(curA,curB);
}
//求长度差
int gap= lenA-lenB;
while(gap--){
    curA=curA->next;
}
//遍历curA和curB 遇到相同则直接返回
while(curA!=NULL){
    if(curA==curB){
		return curA;
    }
    curA=curA->next;
    curB=curB->next;
}
return NULL;

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
        ListNode* curA=headA;
        ListNode* curB=headB;
        int lenA=0,lenB=0;
        while(curA!=NULL){
            lenA++;
            curA=curA->next;
        }
        while(curB!=NULL){
            lenB++;
            curB=curB->next;
        }
        //为什么还要再次赋值，因为上面next到了NULL，懂否，傻子
        curA = headA;
        curB = headB;
        if(lenB>lenA){
            swap(lenA,lenB);
            swap(curA,curB);
        }
        int gap=lenA-lenB;
        //移动
        while(gap){
            curA=curA->next;
            gap--;
        }
        while(curA!=NULL){
            if(curA==curB){
                return curA;
            }
            curA=curA->next;
            curB=curB->next;
        }
        return  NULL;

    }
};