mirror of
https://git.sb/baoshuo/OI-codes.git
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149 lines
3.3 KiB
C++
149 lines
3.3 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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const int to[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
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int n, m, book[705][705];
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bool vis[705][705];
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char g[705][705];
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pair<int, int> y, v, t;
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struct node {
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int x, y, step;
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node()
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: x(0),
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y(0),
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step(0) {}
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node(int _x, int _y)
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: x(_x),
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y(_y),
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step(0) {}
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node(pair<int, int> _point)
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: x(_point.first),
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y(_point.second),
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step(0) {}
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node(pair<int, int> _point, int _step)
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: x(_point.first),
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y(_point.second),
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step(_step) {}
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node(int _x, int _y, int _step)
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: x(_x),
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y(_y),
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step(_step) {}
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};
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/**
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* @brief Preprocess the map
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*/
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void bfsV() {
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memset(vis, 0x00, sizeof(vis));
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memset(book, 0xff, sizeof(book));
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queue<node> q;
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q.push(v);
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vis[v.first][v.second] = true;
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book[v.first][v.second] = 0;
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while (!q.empty()) {
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int now;
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auto u = q.front();
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q.pop();
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// Top
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now = u.x - 1;
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while (now >= 0 && g[now][u.y] != 'I') {
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if (book[now][u.y] == -1) {
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book[now][u.y] = u.step;
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}
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now--;
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}
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// Bottom
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now = u.x + 1;
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while (now < n && g[now][u.y] != 'I') {
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if (book[now][u.y] == -1) {
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book[now][u.y] = u.step;
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}
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now++;
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}
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// Left
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now = u.y - 1;
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while (now >= 0 && g[u.x][now] != 'I') {
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if (book[u.x][now] == -1) {
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book[u.x][now] = u.step;
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}
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--now;
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}
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// Right
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now = u.y + 1;
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while (now < m && g[u.x][now] != 'I') {
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if (book[u.x][now] == -1) {
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book[u.x][now] = u.step;
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}
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now++;
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}
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// Expand
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for (int i = 0; i < 4; i++) {
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node e = node(u.x + to[i][0], u.y + to[i][1], u.step + 1);
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if (e.x >= 0 && e.x < n && e.y >= 0 && e.y < m && g[e.x][e.y] != 'I' && !vis[e.x][e.y]) {
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vis[e.x][e.y] = true;
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q.push(e);
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}
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}
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}
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}
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/**
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* @brief Search path to treasure
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*/
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void bfsY() {
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memset(vis, 0x00, sizeof(vis));
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queue<node> q;
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q.push(node(y, 1));
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while (!q.empty()) {
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auto u = q.front();
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q.pop();
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for (int i = 0; i < 4; i++) {
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node e = node(u.x + to[i][0], u.y + to[i][1], u.step + 1);
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if (e.x >= 0 && e.x < n && e.y >= 0 && e.y < m && e.step <= book[e.x][e.y] && !vis[e.x][e.y]) {
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vis[e.x][e.y] = true;
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// Reached
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if (e.x == t.first && e.y == t.second) {
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cout << "YES" << endl;
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return;
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}
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// Expand
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q.push(e);
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}
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}
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}
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// Can't reach treasure
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cout << "NO" << endl;
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}
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int main() {
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// Read from stdin
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cin >> n >> m;
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for (int i = 0; i < n; i++) {
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cin >> g[i];
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}
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// Mark you, viking and treasure
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < m; j++) {
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if (g[i][j] == 'Y') y = make_pair(i, j);
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if (g[i][j] == 'V') v = make_pair(i, j);
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if (g[i][j] == 'T') t = make_pair(i, j);
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}
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}
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bfsV();
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bfsY();
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return 0;
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}
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