HDU 1026 Ignatius and the Princess I

HDU 1026 Ignatius and the Princess I
http://acm.hdu.edu.cn/showproblem.php?pid=1026

依然是BFS的题目，这次不同的是需要把路径进行记录。计算最短路径的值跟裸题一样，就不重复了，主要的不同是用pre数组把每个点的前一个元素记录下来，最后用迭代的方式把路径输出。

#include<cstdio>#include<queue>#include<cstring>#define INF 10000000using namespace std;char maze[120][120];int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};int dis[120][120];typedef pair<int, int> P;int n, m;P pre[120][120];void bfs(){    queue<P> que;    que.push(P(0, 0));    dis[0][0] = 0;    while(!que.empty()){        P p = que.front();        que.pop();        //if(p.first == n - 1 && p.second == m - 1) break;        for(int i = 0;i < 4;i++){            int nx = p.first + dx[i], ny = p.second + dy[i];            if(nx >= 0 && nx < n && ny >= 0 && ny < m && maze[nx][ny] != 'X'){                if(maze[nx][ny] == '.'){                    if(dis[p.first][p.second] + 1 < dis[nx][ny]){                        dis[nx][ny] = dis[p.first][p.second] + 1;                        pre[nx][ny].first = p.first;                        pre[nx][ny].second = p.second;                        que.push(P(nx, ny));                    }                }                else{                    if(dis[p.first][p.second] + (maze[nx][ny] - '0') + 1 < dis[nx][ny]){                       dis[nx][ny] = dis[p.first][p.second] + (maze[nx][ny] - '0') + 1;                       pre[nx][ny].first = p.first;                       pre[nx][ny].second = p.second;                       que.push(P(nx, ny));                    }                }            }        }    }}void print_pre(int i, int j){    if(pre[i][j].first == -1) return ;    print_pre(pre[i][j].first, pre[i][j].second);    if(maze[i][j] == '.')        printf("%ds:(%d,%d)->(%d,%d)\n",dis[i][j],pre[i][j].first, pre[i][j].second,i, j);    else{        int num = maze[i][j] - '0';        int t = dis[i][j] - num;        printf("%ds:(%d,%d)->(%d,%d)\n",t++, pre[i][j].first, pre[i][j].second, i, j);        for(int k = 1;k <= num;k++){            printf("%ds:FIGHT AT (%d,%d)\n",t++, i, j);        }    }}main(){    while(~scanf("%d %d", &n, &m)){        getchar();        for(int i = 0;i < n;i++){            gets(maze[i]);        }        for(int i = 0;i < n;i++){            for(int j = 0;j < m;j++){                dis[i][j] = INF;            }        }        pre[0][0].first = pre[0][0].second = -1;        bfs();        if(dis[n-1][m-1] == INF)            printf("God please help our poor hero.\n");        else{            printf("It takes %d seconds to reach the target position, let me show you the way.\n",dis[n-1][m-1]);            print_pre(n-1,m-1);        }        puts("FINISH");    }}