複習下C 連結串列操作（雙向迴圈連結串列，查詢迴圈節點）

hhhker發表於2014-11-28

雙向迴圈連結串列  和 單向迴圈連結串列 查詢迴圈節點 思路都是一樣。 快慢指標查詢法。 理論可參考

c 連結串列之 快慢指標 查詢迴圈節點

typedef struct Student_Double
{
    char name[10];
    int  point;
    struct Student_Double *preStu;
    struct Student_Double *nextStu;
} StudentDouble;
StudentDouble *  CreateDoubleCircleLink_Table(){
    
    int i = 0;
    StudentDouble *head = NULL;
    head=(StudentDouble *)malloc(sizeof(StudentDouble));
    head->name[0]='\0';
    head->point = 0;
    head->nextStu = NULL;
    head->preStu = NULL;
    
    //迴圈節點
    StudentDouble *cirleStu = NULL;
    StudentDouble *temp = NULL;
    StudentDouble *currentNode = head;
    while (i<=9) {
        temp = (StudentDouble *)malloc(sizeof(StudentDouble));
        strncpy(temp->name,"Node",sizeof(temp->name));
        temp->point = i;
        temp->nextStu = NULL;
        temp->preStu = currentNode;
        
        currentNode->nextStu = temp;
        currentNode = temp;
        
        if (i==3) {
            cirleStu = currentNode;
        }
        i++;
    }
    //最後 合併迴圈節點
    currentNode->nextStu=cirleStu;
    return head;
}
//已知迴圈節點情況查詢迴圈 連結串列，驗證是否可用
void SelectDoubleLinkTable(StudentDouble *student){
    StudentDouble *next = student->nextStu;
    int i = 0;
    StudentDouble *circleStu = NULL;
    while (next) {
        if (circleStu!=NULL&&next->point == circleStu->point) {
            printf("迴圈節點%d,結束迴圈\n",next->point);
            break;
        }
        if (i==3) {
            circleStu = next;
        }
        printf("index %d; studentName is %s;  point is %d\n",i,next->name,next->point);
        i++;
        next = next->nextStu;
    }


}
//未知情況查詢迴圈節點
StudentDouble * SelectCircleNodeInDoubleLinkTable(StudentDouble *head){
    //快慢指標查詢
    StudentDouble *fast = head;
    StudentDouble *slow = head;
    
    while (fast) {
        fast = fast->nextStu->nextStu;
        slow = slow->nextStu;
        
        if (fast==NULL) {//不是迴圈連結串列推出
            break;
        }
        if (fast==slow) {//快慢指標相遇
            break;
        }
    }
    if (fast == NULL) {
        printf("該連結串列 不是迴圈連結串列\n");
        return NULL;
    }
    
    //查詢迴圈節點
    fast = head;
    while (fast!=slow) {
        fast=fast->nextStu;
        slow=slow->nextStu;
    }
    printf("=====找到迴圈連結串列迴圈節點為%d\n",fast->point);
    return fast;
}
int main(void){
    char sf[15];
  //建立雙向迴圈連結串列
    StudentDouble *head = NULL;

    printf("建立雙向迴圈連結串列Y|N\n");
    scanf("%s",sf);
    if (strcmp(sf,"Y")==0) {
        head = CreateDoubleCircleLink_Table();
    }
    printf("已知情況查詢迴圈連結串列Y|N \n");
    scanf("%s",sf);
    if (strcmp(sf,"Y")==0) {
        SelectDoubleLinkTable(head);
    }
    printf("未知情況查詢迴圈連結串列Y|N \n");
    scanf("%s",sf);
    if (strcmp(sf,"Y")==0) {
        SelectCircleNodeInDoubleLinkTable(head);
    }
    return 0;
}

 

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