题解 | #第一只公共的牛#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 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 headA ListNode类 
     * @param headB ListNode类 
     * @param headC ListNode类 
     * @return ListNode类
     */
    ListNode* findIntersection(ListNode* headA, ListNode* headB, ListNode* headC) {
        // write code here
        for (auto p = headA; p != nullptr; p = p->next) {
            cnt[p->val]++;
        }
        for (auto p = headB; p != nullptr; p = p->next) {
            cnt[p->val]++;
        }
        for (auto p = headC; p != nullptr; p = p->next) {
            cnt[p->val]++;
        }
        for (auto p = headA; p != nullptr; p = p->next) {
            if (cnt[p->val] == 3) return p;
        }
        return nullptr;

    }
    map<int, int> cnt = map<int, int>();

};