BFS算法之求可以走的块数

#include <iostream>
#include <vector>
#include <algorithm>
#include <stdlib.h>
#include <string>
#include <queue>
using namespace std;
#define maxn 100
struct node
{
	int x, y;
};
node Node;
int n, m;
int matrix[maxn][maxn];
bool inq[maxn][maxn] = { false };
int X[4] = {0,0,1,-1};
int Y[4] = {1,-1,0,0};
bool judge(int x, int y)//函数用于判断什么样的元素需要压入队列中
{
	if (x >= n || x < 0 || y >= m || y < 0)
		return false;
    if (inq[x][y] == true||matrix[x][y] == 0)
		return false;
		
	return true;
}
void BFS(int x, int y)
{
	queue<node> q;
	Node.x = x;
	Node.y = y;
	q.push(Node);//stl容器中的queue：压入的是一个副本而非引用，改版x或y不会影响压入的数据
	inq[x][y] = true;//dont forget the judge flag
	while (!q.empty())
	{
		node top = q.front();//you can directlt use "="
		q.pop();
		for (int i = 0; i < 4; i++)
		{
			int newx = top.x + X[i];
			int newy = top.y + Y[i];

			if (judge(newx, newy) == true)
			{
				Node.x = newx;
				Node.y = newy;
				q.push(Node);//注意：每入队一个元素，其标记就改变。
				inq[newx][newy] = true;
			}
		}
	}
}
int main()
{
	cin >> n >> m;
	for(int x = 0;x < n;x++)
		for (int y = 0; y < m; y++)
		{
			cin >> matrix[x][y];
		}
	int num = 0;
	for (int x = 0; x < n; x++)
		for (int y = 0; y < m; y++)
		{
			if (matrix[x][y] == 1 && inq[x][y] == false)
			{
				num++;
				BFS(x, y);
			}
		}
	cout << num<<endl;
}