mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-25 05:51:58 +00:00
182 lines
3.9 KiB
C++
182 lines
3.9 KiB
C++
#include <iostream>
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#include <cstring>
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#include <queue>
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#include <string>
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#include <utility>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 505;
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const int INF = 0x3f3f3f3f;
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const int d[][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
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int n, m, s, t, pos[N * N][4], dist1[N][N], dist2[N * N];
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std::string h[N];
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std::vector<std::pair<int, int>> g[N * N];
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bool vis[N * N];
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int id(int x, int y) {
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return x * m + y;
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}
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void spfa() {
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memset(dist2, 0x3f, sizeof(dist2));
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std::queue<int> q;
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q.emplace(s);
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dist2[s] = 0;
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vis[s] = true;
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while (!q.empty()) {
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int u = q.front();
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q.pop();
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vis[u] = false;
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for (auto e : g[u]) {
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int v = e.first;
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long long w = e.second;
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if (dist2[v] > dist2[u] + w) {
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dist2[v] = dist2[u] + w;
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if (!vis[v]) {
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vis[v] = true;
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q.emplace(v);
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}
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}
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}
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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memset(dist1, 0x3f, sizeof(dist1));
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cin >> n >> m;
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for (int i = 1; i <= n; i++) {
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cin >> h[i];
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h[i] = ' ' + h[i];
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (h[i][j] == 'C') {
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s = id(i, j);
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} else if (h[i][j] == 'F') {
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t = id(i, j);
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (h[i][j - 1] == '#') {
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pos[id(i, j)][0] = id(i, j);
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} else {
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pos[id(i, j)][0] = pos[id(i, j - 1)][0];
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = m; j; j--) {
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if (h[i][j + 1] == '#') {
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pos[id(i, j)][1] = id(i, j);
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} else {
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pos[id(i, j)][1] = pos[id(i, j + 1)][1];
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (h[i - 1][j] == '#') {
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pos[id(i, j)][2] = id(i, j);
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} else {
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pos[id(i, j)][2] = pos[id(i - 1, j)][2];
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}
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}
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}
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for (int i = n; i; i--) {
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for (int j = 1; j <= m; j++) {
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if (h[i + 1][j] == '#') {
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pos[id(i, j)][3] = id(i, j);
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} else {
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pos[id(i, j)][3] = pos[id(i + 1, j)][3];
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}
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}
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}
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std::queue<std::pair<int, int>> q;
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (h[i][j] == '#') {
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q.emplace(i, j);
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dist1[i][j] = 0;
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}
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}
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}
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while (!q.empty()) {
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int x = q.front().first,
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y = q.front().second;
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q.pop();
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for (auto d : d) {
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int xx = x + d[0],
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yy = y + d[1];
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if (xx < 1 || xx > n || yy < 1 || yy > m || h[xx][yy] == '#') continue;
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if (dist1[xx][yy] > dist1[x][y] + 1) {
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dist1[xx][yy] = dist1[x][y] + 1;
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q.emplace(xx, yy);
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (h[i][j] == '#') continue;
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for (auto d : d) {
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int x = i + d[0],
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y = j + d[1];
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if (h[x][y] != '#') {
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g[id(i, j)].emplace_back(id(x, y), 1);
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}
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}
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for (int k = 0; k < 4; k++) {
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if (pos[id(i, j)][k] != id(i, j)) {
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g[id(i, j)].emplace_back(pos[id(i, j)][k], dist1[i][j]);
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}
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}
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}
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}
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spfa();
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if (dist2[t] == INF) {
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cout << "nemoguce" << endl;
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} else {
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cout << dist2[t] << endl;
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}
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return 0;
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}
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