6.4.2 走迷宫

bfs 最短路径

#include<cstdio>
#include<cstring>
#include<iostream>
#include<string>
#include<algorithm>
#include<queue>
using namespace std;
const int N=105;
int n, m, rs, cs, rt, ct;
typedef int A[N][N];
A maze, vis, dist, last_dir;

int dr[] = {-1,1,0,0};
int dc[] = {0,0,-1,1};
char name[] = "UDLR";

struct Pos {
    Pos(int r=0, int c=0): r(r), c(c) {}
    bool operator == ( const Pos& rhs) {
        return r==rhs.r && c==rhs.c;
    }
    bool operator != ( const Pos& rhs) {
        return !(*this==rhs);
    }
    int r;
    int c;
};

Pos fa[N][N];

void bfs() {
    queue<Pos> q;
    Pos s=Pos(rs, cs);
    q.push(s);
    vis[rs][cs]=1; dist[rs][cs]=0; fa[rs][cs]=s;
    while(!q.empty()) {
        Pos t=q.front(); q.pop();
        if(t.r==rt && t.c==ct)
            return;
        for(int i=0;i<4;i++) {
            int nr,nc;
            nr=t.r+dr[i]; 
            nc=t.c+dc[i]; 
            if(nr>=0 && nr<n && nc>=0 && nc< m && maze[nr][nc] && !vis[nr][nc]) {
                vis[nr][nc]=1;
                dist[nr][nc]=dist[t.r][t.c]+1;
                fa[nr][nc]=t;
                last_dir[nr][nc]=i;
                q.push(Pos(nr, nc));
            }
        }
    }
}

void print_path(const Pos& p) {
    if(fa[p.r][p.c]!=p) {
        print_path(fa[p.r][p.c]);
        printf("%c", name[last_dir[p.r][p.c]]);
    }
}

void dump_dist() {
    printf("%s
", __FUNCTION__);
    for(int i=0;i<n;i++) {
        for(int j=0;j<m;j++)
            printf("%2d ", dist[i][j]);
        printf("
");
    }
    printf("
");
}

int main()
{
    freopen("./maze.in", "r", stdin);
    scanf("%d%d%d%d%d%d", &n, &m, &rs, &cs, &rt, &ct);
    for(int i=0;i<n;i++)
        for(int j=0;j<m;j++)
            scanf("%d", &maze[i][j]);
    bfs();
    dump_dist();
    print_path(Pos(rt, ct));

    return 0;
}

 

lrj代码：  坐标转换思想可取

#include<stdio.h>
#include<string.h>
#define MAXN 105
int n, m, xs, ys, xt, yt;
int maze[MAXN][MAXN], vis[MAXN][MAXN], fa[MAXN][MAXN], dist[MAXN][MAXN], last_dir[MAXN][MAXN], num[MAXN][MAXN];

int dx[] = {-1,1,0,0};
int dy[] = {0,0,-1,1};
char name[] = "UDLR";

int q[MAXN*MAXN];
void bfs(int x, int y) {
  int front=0, rear=0, d, u;
  u = x*m+y;
  vis[x][y] = 1; fa[x][y] = u; dist[x][y] = 0;
  q[rear++] = u;
  while(front<rear) {
    u = q[front++];    
    x = u/m; y = u%m;
    for(d = 0; d < 4; d++) {
      int nx = x+dx[d], ny = y+dy[d];
      if(nx>=0 && nx<n && ny>=0 && ny<m && maze[nx][ny] && !vis[nx][ny]) {
        int v = nx*m+ny;
        q[rear++] = v;
        vis[nx][ny] = 1;
        fa[nx][ny] = u;
        dist[nx][ny] = dist[x][y]+1;
        last_dir[nx][ny] = d;
      }
    }
  }
}

void print_path(int x, int y) {
  int fx = fa[x][y]/m;
  int fy = fa[x][y]%m;
  if(fx != x || fy != y) {
    print_path(fx, fy);
    putchar(name[last_dir[x][y]]);
  }
}

int dir[MAXN*MAXN];
void print_path2(int x, int y) {
  int c = 0;
  for(;;) {
    int fx = fa[x][y]/m;
    int fy = fa[x][y]%m;
    if(fx == x && fy == y) break;
    dir[c++] = last_dir[x][y];
    x = fx;
    y = fy;
  }
  while(c--)
    putchar(name[dir[c]]);
}

int main() {
  int i, j;
  scanf("%d%d%d%d%d%d", &n, &m, &xs, &ys, &xt, &yt);
  for(i = 0; i < n; i++)
    for(j = 0; j < m; j++)
      scanf("%d", &maze[i][j]);
  memset(vis, 0, sizeof(vis));
  bfs(xs, ys);
  print_path(xt, yt);
  putchar('
');
  print_path2(xt, yt);
  putchar('
');
  return 0;
}