POJ_4127（用栈和队列实现的BFS算法）

POJ_4127，用栈和队列实现BFS迷宫题目，但二维数组仍更常用

#include <iostream>
#include <queue>
#include <stack>
using namespace std;
bool canotwalk[5][5];
struct point{
	int i,j,distance;
}points[5][5];
queue<point> road;
stack<point> antiroad;

void update(point curr,int i,int j){
	if(canotwalk[i][j])		points[i][j].distance=-1;
	else if(!points[i][j].distance){
		points[i][j].distance=curr.distance+1;
		road.push(points[i][j]);
	}
}

int main(){
	int length;
	for(int i=0;i<5;i++)
		for(int j=0;j<5;j++)
			cin>>canotwalk[i][j];
	for(int i=0;i<5;i++)
		for(int j=0;j<5;j++){
			points[i][j].distance=0;
			points[i][j].i=i;
			points[i][j].j=j;
		}
	points[0][0].distance=1;
	road.push(points[0][0]);
	while(!road.empty()){
		point curr=road.front();
		road.pop();
		if(curr.i==4 && curr.j==4){
			length=curr.distance;
			break;
		}
		if(curr.i>0)	update(curr,curr.i-1,curr.j);
		if(curr.i<4)	update(curr,curr.i+1,curr.j);
		if(curr.j>0)	update(curr,curr.i,curr.j-1);
		if(curr.j<4)	update(curr,curr.i,curr.j+1);
	}
	antiroad.push(points[4][4]);
	while(1){
		point curr=antiroad.top();
		if(curr.distance==1){
			while(!antiroad.empty()){
				point temp=antiroad.top();
				antiroad.pop();
				cout<<"("<<temp.i<<", "<<temp.j<<")"<<endl;		
			}
			return 0;
		}
		if(curr.i>0 && points[curr.i-1][curr.j].distance==curr.distance-1)
			antiroad.push(points[curr.i-1][curr.j]);
		if(curr.i<4 && points[curr.i+1][curr.j].distance==curr.distance-1)
			antiroad.push(points[curr.i+1][curr.j]);
		if(curr.j>0 && points[curr.i][curr.j-1].distance==curr.distance-1)
			antiroad.push(points[curr.i][curr.j-1]);
		if(curr.j<4 && points[curr.i][curr.j+1].distance==curr.distance-1)
			antiroad.push(points[curr.i][curr.j+1]);
	}
}