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Codeforces Round 871 (Div. 4)/E. The Lakes.cpp

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+/* Problem URL: https://codeforces.com/contest/1829/problem/E */
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (size_t i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (size_t i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+int n, m;
+
+vvl grid;
+V<V<bool>> vis;
+
+ll dfs(int i, int j)
+{
+    vis[i][j] = true;
+
+    int add[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    ll ans = 0;
+
+    for (auto &k : add) {
+        int id = i + k[0];
+        int jd = j + k[1];
+
+        if (id >= 0 && id < n && jd >= 0 && jd < m && !vis[id][jd] && grid[id][jd] != 0) {
+            ans += dfs(id, jd);
+        }
+    }
+
+    return ans + grid[i][j];
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int t;
+    cin >> t;
+    while (t--) {
+        cin >> n >> m;
+
+        vis.assign(n, V<bool>(m, false));
+        grid.assign(n, vl(m));
+
+
+        cin >> grid;
+        ll ans = 0;
+
+        rep(i, n) {
+            rep(j, m) {
+                if (grid[i][j] != 0) {
+                    rmax(ans, dfs(i, j));
+                }
+            }
+        }
+
+        cout << ans << '\n';
+    }
+}