atcoder/abc020C

Author: xirc

atcoder/abc020/C/main.cpp

@@ -0,0 +1,79 @@
+#include <bits/stdc++.h>
+
+inline int64_t binary_search(
+    std::function<bool(int64_t)> const& predicate,
+    int64_t ng,
+    int64_t ok
+) {
+    assert(!predicate(ng) && predicate(ok));
+    while (abs(ok - ng) > 1) {
+        auto m = (ok + ng) / 2;
+        if (predicate(m)) ok = m;
+        else ng = m;
+    }
+    return ok;
+}
+
+using namespace std;
+using ll = int64_t;
+using ff = long double;
+
+int H, W, T;
+vector<string> M;
+int sX, sY, gX, gY;
+
+vector<int> dx = { 1, -1, 0, 0 };
+vector<int> dy = { 0, 0, 1, -1 };
+bool pass(ll XX) {
+    priority_queue<array<ll,3>> Q;
+    vector<vector<bool>> done(H, vector<bool>(W, false));
+    Q.push({ 0, sX, sY });
+    while (Q.size()) {
+        auto entry = Q.top(); Q.pop();
+        ll t = -entry[0];
+        int x = entry[1], y = entry[2];
+        if (done[y][x]) continue;
+        done[y][x] = true;
+        for (int i = 0; i < 4; ++i) {
+            int nx = x + dx[i], ny = y + dy[i];
+            if (nx < 0 || nx >= W) continue;
+            if (ny < 0 || ny >= H) continue;
+            if (done[ny][nx]) continue;
+            if (nx == gX && ny == gY) {
+                return t + 1 <= T;
+            }
+            ll nt = t + (M[ny][nx] == '.' ? 1 : XX);
+            Q.push({ -nt, nx, ny });
+        }
+    }
+    return false;
+}
+
+ll solve() {
+    for (int y = 0; y < H; y++) {
+        for (int x = 0; x < W; x++) {
+            if (M[y][x] == 'S') {
+                sX = x, sY = y;
+            }
+            if (M[y][x] == 'G') {
+                gX = x, gY = y;
+            }
+        }
+    }
+    ll ng = T + 1, ok = 1;
+    return binary_search(pass, ng, ok);
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    cin >> H >> W >> T;
+    M.assign(H, "");
+    for (int y = 0; y < H; ++y) {
+        cin >> M[y];
+    }
+    cout << solve() << endl;
+
+    return 0;
+}