同一个S可能需要多次经过,只需杀一次。
#define _CRT_SECURE_NO_WARNINGS
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
const int N = 100 + 5;
char s[N][N];
int si, sj, n, m, ei, ej, p[N][N];
struct Node {
int x, y, key, dis, snack;
Node(int x = 0, int y = 0, int key = 0, int dis = 0, int snack = 0) :x(x), y(y), key(key), dis(dis), snack(snack) {}
bool operator<(const Node& n)const {
return dis > n.dis;
}
};
int dir[][4] = { {-1,1,0,0},{0,0,-1,1} };
int d[N][N][10];
int bfs() {
priority_queue<Node> q;
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
for (int k = 0; k <= m; k++)
d[i][j][k] = 0x3f3f3f3f;
q.push(Node(si, sj, 0, 0, 0));
d[si][sj][0] = 0;
while (!q.empty()) {
Node tp = q.top();
q.pop();
for (int i = 0; i < 4; i++) {
int ii = tp.x + dir[0][i];
int jj = tp.y + dir[1][i];
if (0 <= ii && ii < n && 0 <= jj && jj < n && s[ii][jj] != '#') {
if (s[ii][jj] == 'S') {
if ((tp.snack >> p[ii][jj]) & 1)
{
if (tp.dis + 1 < d[ii][jj][tp.key])
d[ii][jj][tp.key] = tp.dis + 1, q.push(Node(ii, jj, tp.key, tp.dis + 1, tp.snack));
}
else {
if (tp.dis + 2 < d[ii][jj][tp.key])
d[ii][jj][tp.key] = tp.dis + 2, q.push(Node(ii, jj, tp.key, tp.dis + 2, tp.snack | (1 << p[ii][jj])));
}
}
else if ('1' <= s[ii][jj] && s[ii][jj] <= '9') {
if (s[ii][jj] - '0' == tp.key + 1) {
if (tp.dis + 1 < d[ii][jj][tp.key + 1]) {
d[ii][jj][tp.key + 1] = tp.dis + 1, q.push(Node(ii, jj, tp.key + 1, tp.dis + 1, tp.snack));
}
}
else {
if (tp.dis + 1 < d[ii][jj][tp.key])
d[ii][jj][tp.key] = tp.dis + 1, q.push(Node(ii, jj, tp.key, tp.dis + 1, tp.snack));
}
}
else if (s[ii][jj] == 'T') {
if (tp.key == m)
return tp.dis + 1;
else{
if (tp.dis + 1 < d[ii][jj][tp.key])
d[ii][jj][tp.key] = tp.dis + 1, q.push(Node(ii, jj, tp.key, tp.dis + 1, tp.snack));
}
}
else {
if (tp.dis + 1 < d[ii][jj][tp.key])
d[ii][jj][tp.key] = tp.dis + 1, q.push(Node(ii, jj, tp.key, tp.dis + 1, tp.snack));
}
}
}
}
return -1;
}
int main(){
for (; scanf("%d%d", &n, &m) == 2 && n + m;) {
si = -1, sj = -1, ei = -1, ej = -1;
for (int i = 0; i < n; i++)
scanf("%s", s[i]);
int cnt = 0;
for(int i=0;i<n;i++)
for (int j = 0; j < n; j++)
{
if (s[i][j] == 'K')
si = i, sj = j;
else if (s[i][j] == 'T')
ei = i, ej = j;
else if (s[i][j] == 'S')
p[i][j] = cnt++;
}
if (ei == -1 || si == -1) {
printf("impossible\n");
}
else {
int ans = bfs();
if (ans != -1) printf("%d\n", ans);
else printf("impossible\n");
}
}
return 0;
}