uva 816 - Abbott's Revenge（bfs）

题目链接：uva 816 - Abbott's Revenge

bfs，将每个点拆成四个点建图。

#include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;
const int maxn = 30;
const int dir[4][2] = {{0, -1}, {-1, 0}, {0, 1}, {1, 0}};
typedef pair<int,int> pii;

struct State {
int x, y, d, pre;
State (int x = 0, int y = 0, int d = 0, int pre = 0): x(x), y(y), d(d), pre(pre) {}
}Q[100000];

map<char, int> M;
int Sx, Sy, Ex, Ey, vis[maxn][maxn][5];
char s[maxn], o[maxn], t[maxn];
vector<int> G[maxn][maxn][5];
vector<pii> ans;

void add (int x, int y, char* p) {
int n = strlen(p);
int d = M[p[0]];
for (int i = 1; i < n; i++)
G[x][y][d].push_back((d + M[p[i]]) % 4);
}

void init () {
memset(vis, 0, sizeof(vis));
for (int i = 0; i < maxn; i++) {
for (int j = 0; j < maxn; j++)
for (int x = 0; x < 4; x++)
G[i][j][x].clear();
}
scanf("%d%d%s%d%d", &Sx, &Sy, o, &Ex, &Ey);
int x, y;
while (scanf("%d", &x) == 1 && x) {
scanf("%d", &y);
while (scanf("%s", t) == 1 && t[0] != '*')
add(x, y, t);
}
}

void put(int p) {
if (p == -1) return;
put(Q[p].pre);
ans.push_back(make_pair(Q[p].x, Q[p].y));
}

void bfs () {
int head = 0, rear = 0, Sd = M[o[0]];
ans.clear();
G[Sx][Sy][Sd].push_back(Sd);
Q[rear++] = State(Sx, Sy, Sd, -1);
vis[Sx][Sy][Sd] = 1;

while (head < rear) {
State u = Q[head++];
int x = u.x, y = u.y, d = u.d;

if (x == Ex && y == Ey) {
put(head-1);
for (int i = 0; i < ans.size(); i++) {
if (i % 10 == 0) printf("\n ");
printf(" (%d,%d)", ans[i].first, ans[i].second);
}
printf("\n");
return;
}

for (int i = 0; i < G[x][y][d].size(); i++) {
int v = G[x][y][d][i];
int p = x + dir[v][0];
int q = y + dir[v][1];

if (vis[p][q][v]) continue;
vis[p][q][v] = 1;
Q[rear++] = State(p, q, v, head-1);
}
}
printf("\n No Solution Possible\n");
}

int main () {
M['W'] = 0, M['N'] = 1, M['E'] = 2, M['S'] = 3;
M['R'] = 1, M['F'] = 0, M['L'] = 3;
while (scanf("%s", s) == 1 && strcmp(s, "END")) {
init ();
printf("%s", s);
bfs();
}
return 0;
}