P1902 刺杀大使

R63984704

Luogu/P1902/P1902.cpp

@@ -0,0 +1,56 @@
+#include <bits/stdc++.h>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+const int nxt[4][2] = {{0, -1}, {0, 1}, {1, 0}, {-1, 0}};
+
+int n, m, l, r, ans, g[1005][1005];
+bool vis[1005][1005];
+
+bool bfs(int x, int y, int k) {
+    memset(vis, 0x00, sizeof(vis));
+    std::queue<std::pair<int, int>> q;
+    q.push(std::make_pair(x, y));
+    vis[x][y] = true;
+    while (!q.empty()) {
+        auto t = q.front();
+        q.pop();
+        for (int i = 0; i < 4; i++) {
+            int nx = t.first + nxt[i][0];
+            int ny = t.second + nxt[i][1];
+            if (nx < 1 || nx > n || ny < 1 || ny > m) continue;
+            if (vis[nx][ny]) continue;
+            if (g[nx][ny] > k) continue;
+            vis[nx][ny] = true;
+            if (nx == n) return true;
+            q.push(std::make_pair(nx, ny));
+        }
+    }
+    return false;
+}
+
+int main() {
+    l = std::numeric_limits<int>::max();
+    r = std::numeric_limits<int>::min();
+    cin >> n >> m;
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            cin >> g[i][j];
+            l = std::min(l, g[i][j]);
+            r = std::max(r, g[i][j]);
+        }
+    }
+    while (l <= r) {
+        int mid = l + r >> 1;
+        if (bfs(1, 1, mid)) {
+            r = mid - 1;
+            ans = mid;
+        } else {
+            l = mid + 1;
+        }
+    }
+    cout << ans << endl;
+    return 0;
+}