Bfs1.5(打印路径)

打印左顶点到右低点最短路径

http://poj.org/problem?id=3984

输入:

0 1 0 0 0
0 1 0 1 0
0 0 0 0 0
0 1 1 1 0
0 0 0 1 0

输出:

(0, 0)
(1, 0)
(2, 0)
(2, 1)
(2, 2)
(2, 3)
(2, 4)
(3, 4)
(4, 4)

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
#include<stack>
using namespace std;
int maze[10][10];
int visit[10][10],dist[10][10];
int dr[]= {-1,1,0,0}; //上,下,左,右
int dc[]= {0,0,-1,1};
struct Node
{
    int r,c;//也可以在Node中加一个int pre属性,然后做一个全局的nodes,就不用pre[][]数组了.
    Node(int r,int c):r(r),c(c) {}
    Node() {}
} pre[10][10];
queue<Node> Q;
void bfs()
{
    while(!Q.empty())Q.pop();
    memset(visit,0,sizeof(visit));
    dist[0][0]=0;
    visit[0][0]=1;
    Q.push(Node(0,0));
    while(!Q.empty())
    {
        Node node =Q.front();
        Q.pop();
        int r=node.r;
        int c=node.c;//记录前驱节点;
        for(int i=0; i<4; i++)
        {
            int nr=node.r+dr[i];
            int nc=node.c+dc[i];
            if(nr>=0&&nr<5&&nc>=0&&nc<5&&visit[nr][nc]==0&&maze[nr][nc]==0)
            {
                visit[nr][nc]=1;
                Q.push(Node(nr,nc));
                dist[nr][nc]=1+dist[r][c];
                pre[nr][nc]=Node(r,c);
                if(nr==4&&nc==4)return ;
            }
        }
    }

}
int main()
{
    for(int i=0;i<5;i++)
        for(int j=0;j<5;j++)
            scanf("%d",&maze[i][j]);
    bfs();
    stack<Node> S;
    int cur_r=4,cur_c=4;
    while(true)
    {
        S.push(Node(cur_r,cur_c));
        if(cur_c==0&&cur_r==0)break;
        int r=cur_r;
        int c=cur_c;
        cur_r=pre[r][c].r;
        cur_c=pre[r][c].c;
        //cur_r、c记录前驱节点;
        //再找前驱节点的前驱节点;
    }
    while(!S.empty())
    {
        Node node=S.top(); S.pop();
        printf("(%d, %d)\n",node.r,node.c);
    }
    return 0;
}