BFS (Simple implementation based on C language)

BFS (Simple implementation based on C language)

• Put the root node at the end of the queue

• Each time an element is taken from the head of the queue, all the next level elements of this element are checked, and they are placed at the end of the queue. And mark this element as the predecessor of its next element

• End the program when the element you are looking for is found

• If traversing the entire tree and not finding it, end the program

#include<stdio.h>
#include<stdlib.h>
#define MAX_VALUE 4
int visit[MAX_VALUE];
typedef struct ArcNode
{
	int adjvex;
	struct ArcNode*nextarc;
}ArcNode;
typedef struct VNode
{
	int data;
	ArcNode*firstarc;
}VNode,AdjList[MAX_VALUE];
typedef struct
{
	AdjList vertices;
	int vexnum, arcnum;
}ALGraph;
typedef struct queue
{
	int *pBase;
	int front, rear;
}QUEUE;
int LocateVex(ALGraph G, int v);
void CreatUDG(ALGraph *G);
void PrintUDG(ALGraph G);
void init_queue(QUEUE*Q);
bool isfull_queue(QUEUE*Q);
bool isempty_queue(QUEUE*Q);
void in_queue(QUEUE*Q,int val);
int out_queue(QUEUE*Q);
void BFS(ALGraph G,QUEUE*Q);
void BFST(ALGraph G, QUEUE *Q);
int main()
{
	ALGraph G;
	QUEUE Q;
	CreatUDG(&G);
	PrintUDG(G);
	BFST(G, &Q);
	return 0;
}
int LocateVex(ALGraph G, int v)
{
	for (int i = 0; i < G.vexnum; i++)
	{
		if (G.vertices[i].data == v)
		{
			return i;
		}
	}
}
void CreatUDG(ALGraph *G)
{
	ArcNode*p, *q;
	int i, j, v1, v2;
	printf("分别输入顶点个数和边的个数：\n");
	scanf("%d%d", &(G->vexnum), &(G->arcnum));
	printf("请输入各个顶点的值：\n");
	for (int i = 0; i < G->vexnum; i++)
	{
		scanf("%d", &(G->vertices[i].data));
		G->vertices[i].firstarc = NULL;
	}
	printf("分别输入各条边的两个顶点：\n");
	for (int k = 0; k < G->arcnum; k++)
	{
		scanf("%d%d", &v1, &v2);
		i = LocateVex(*G, v1);
		j = LocateVex(*G, v2);
		p = (ArcNode*)malloc(sizeof(ArcNode));
		p->adjvex = j;
		p->nextarc = NULL;
		p->nextarc = G->vertices[i].firstarc;
		G->vertices[i].firstarc = p;
		q = (ArcNode*)malloc(sizeof(ArcNode));
		q->adjvex = i;
		q->nextarc = NULL;
		q->nextarc = G->vertices[j].firstarc;
		G->vertices[j].firstarc = q;
	}
}
void PrintUDG(ALGraph G)
{
	ArcNode*p = NULL;
	for (int i = 0; i < G.vexnum; i++)
	{
		printf("第%d条边\n", i + 1);
		p = G.vertices[i].firstarc;
		while (p != NULL)
		{
			printf("%d  ", (p->adjvex) + 1);
			p = p->nextarc;
		}
		printf("\n");
	}
}
void init_queue(QUEUE*Q)
{
	Q->pBase = (int*)malloc((sizeof(int))*4);
	Q->front = 0;
	Q->rear = 0;
}
bool isfull_queue(QUEUE*Q)
{ 
	if (((Q->rear + 1) % MAX_VALUE) == Q->front)
	{
		return true;
	}
	else
		return false;
}
bool isempty_queue(QUEUE*Q)
{
	if (Q->rear == Q->front)
	{
		return true;
	}
	else
		return false;
}
void in_queue(QUEUE*Q, int val)
{
	if (isfull_queue(Q))
	{
		return;
	}
	Q->pBase[Q->rear] = val;
	Q->rear = (Q->rear + 1) % MAX_VALUE;
	//printf("入对元素为%d\n", val);
}
int out_queue(QUEUE*Q)
{
	int temp = 0;
	if (isempty_queue(Q))
		return 0;
	temp = Q->pBase[Q->front];
	Q->front = (Q->front + 1) % MAX_VALUE;
	//printf("\n返回的值为%d\n", temp);
	return temp;
}
void BFS(ALGraph G,QUEUE*Q)
{
	init_queue(Q);
	//自己总结：  注意  下面的这两条语句要放在开头或者在下面的for循环里面在加上条件
	//判断visit数组是否访问过  否则就会当while循环退出的时候 就会继续执行printf("%d  ", G.vertices[i].data)
	//会导致多输出结果
	visit[0] = 1;
	printf("%d  ", G.vertices[0].data);
	for (int i = 0; i < G.vexnum; i++)
	{
		//visit[i] = 1;
		//printf("%d  ", G.vertices[i].data);
		in_queue(Q,i);
		while (!isempty_queue(Q))
		{
			int temp=out_queue(Q);
			ArcNode*p = G.vertices[temp].firstarc;
			while (p!=NULL)
			{
				if (visit[p->adjvex]==0)
				{
					visit[p->adjvex] = 1;
					printf("%d  ", G.vertices[p->adjvex].data);
					in_queue(Q, p->adjvex);
				}
				p = p->nextarc;
			}
		}
	}
}
void BFST(ALGraph G, QUEUE *Q)
{
	for (int i = 0; i < G.vexnum; i++)
	{
		if (!visit[i])
		{
			BFS(G, Q);
		}
	}
}