【力扣 简单 C】160. 相交链表

目录

题目

解法一：哈希集合

解法二：双指针

题目

解法一：哈希集合

typedef struct hashSetListNode
{
    void* val;
    struct hashSetListNode* next;
} hashSetListNodeType;
 
typedef struct hashSet
{
    hashSetListNodeType** bucket;
    uint32_t size;
} hashSetType;
 
hashSetType* hashSetInit(uint32_t size)
{
    hashSetType* hashSet = malloc(sizeof(*hashSet));
    hashSet->bucket = calloc(size, sizeof(*hashSet->bucket));
    hashSet->size = size;
    return hashSet;
}

// FNV-1a
uint32_t hash(const uint8_t* data, uint32_t len)
{
    uint32_t hash = 0x811c9dc5;
    for (int i = 0; i < len; i++)
    {
        hash ^= data[i];
        hash *= 0x01000193;
    }
    return hash;
}
 
void hashSetInsert(hashSetType* hashSet, void* val)
{
    uint32_t index = hash((uint8_t*)&val, sizeof(val)) % hashSet->size;
    hashSetListNodeType* newNode = malloc(sizeof(*newNode));
    newNode->val = val;
    newNode->next = hashSet->bucket[index];
    hashSet->bucket[index] = newNode;
}
 
void* hashSetFind(hashSetType* hashSet, void* val)
{
    uint32_t index = hash((uint8_t*)&val, sizeof(val)) % hashSet->size;
    hashSetListNodeType* curNode = hashSet->bucket[index];
    while (curNode)
    {
        if (curNode->val == val)
            return val;
        curNode = curNode->next;
    }
    return NULL;
}
 
void hashSetFree(hashSetType* hashSet)
{
    for (int i = 0; i < hashSet->size; i++)
    {
        hashSetListNodeType* freeNode = hashSet->bucket[i];
        while (freeNode)
        {
            hashSetListNodeType* nextNode = freeNode->next;
            free(freeNode);
            freeNode = nextNode;
        }
    }
    free(hashSet->bucket);
    free(hashSet);
}
 
struct ListNode* find(struct ListNode* head1, struct ListNode* head2)
{
    hashSetType* hashSet = hashSetInit(512);
    struct ListNode* list1CurNode = head1;
    struct ListNode* list2CurNode = head2;
 
    while (list1CurNode)
    {
        hashSetInsert(hashSet, list1CurNode);
        list1CurNode = list1CurNode->next;
    }
 
    while (list2CurNode)
    {
        if (hashSetFind(hashSet, list2CurNode))
            break;
        list2CurNode = list2CurNode->next;
    }
    hashSetFree(hashSet);
    return list2CurNode;
}
 
struct ListNode* getIntersectionNode(struct ListNode* headA, struct ListNode* headB)
{
    return find(headA, headB);
}

解法二：双指针

struct ListNode* find(struct ListNode* head1, struct ListNode* head2)
{
    struct ListNode* list1CurNode = head1;
    struct ListNode* list2CurNode = head2;
    while (list1CurNode != list2CurNode)
    {
        list1CurNode = list1CurNode ? list1CurNode->next : head2;
        list2CurNode = list2CurNode ? list2CurNode->next : head1;
    }
    return list1CurNode;
}

struct ListNode *getIntersectionNode(struct ListNode *headA, struct ListNode *headB)
{
    return find(headA, headB);
}