#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>/*/*给你一个整数数组 nums 。
如果一组数字(i, j) 满足 nums[i] == nums[j] 且 i < j ，就可以认为这是一组 好数对 。
返回好数对的数目。int numIdenticalPairs(int* arr, int n)
{int i = 0;int count = 0;for (i = 0; i < n; i++){int start = arr[i];int j = 0;for (j = i + 1; j < n; j++){if (arr[j] == start){count++;continue;}}}return count;
}int main()
{int array[100] = {0};int n;scanf("%d", &n);int i = 0;for (i = 0; i < n; i++){scanf("%d", &array[i]);}numIdenticalPairs(array, n);return 0;
}*/typedef int datatype;typedef struct tree
{datatype data;struct tree* left;struct tree* right;
}tree;typedef struct list
{tree* data;struct list* next;
}list;typedef struct queue
{list* front;list* rear;
}queue;void initqueue(queue* q)
{q->front = q->rear = (list*)malloc(sizeof(list));if (q->front == NULL){printf("NULL\n");return;}q->front->next = NULL;
}bool isempty(queue* q)
{if (q->front == q->rear || q->front->next == NULL){return true;}return false;
}void inqueue(queue* q, tree* root)
{list* newnode = (list*)malloc(sizeof(list));if (newnode == NULL){printf("NULL\n");return;}newnode->data = root;newnode->next = NULL;q->rear->next = newnode;q->rear = newnode;
}tree* outqueue(queue* q)
{list* pointer;tree* temp;pointer = q->front->next;temp = pointer->data;q->front->next = pointer->next;if (q->front->next == NULL){q->rear = q->front;}free(pointer);pointer = NULL;return temp;
}void visit(tree* pointer)
{printf("%d ", pointer->data);
}tree* creattree(tree* root)
{datatype element;scanf("%d", &element);if (element != 0){root = (tree*)malloc(sizeof(tree));if (root == NULL){printf("NULL\n");exit(1);}root->data = element;root->left = NULL;root->right = NULL;root->left = creattree(root->left);root->right = creattree(root->right);}return root;
}void preorder(tree* root)
{queue q;initqueue(&q);tree* pointer = root;inqueue(&q, root);while (!isempty(&q)){pointer = outqueue(&q);visit(pointer);if (pointer->left != NULL){inqueue(&q, pointer->left);}if (pointer->right != NULL){inqueue(&q, pointer->right);}}
}int main()
{printf("请输入节点值\n");tree* root = NULL;root = creattree(root);preorder(root);return 0;
}