Create CEOI 21-stones.cpp

Author: dolphingarlic

CEOI/CEOI 21-stones.cpp

@@ -0,0 +1,51 @@
+/*
+CEOI 2021 Stones
+- Basically, you choose stones and piles so that Branko
+  must always take 1 stone, and there is either an even
+  number of single-stone piles when he has to pick from
+  a pile or there's at least one pile with >1 stone.
+*/
+
+#include <iostream>
+#include <set>
+using namespace std;
+
+int a[501];
+
+int main() {
+    int n;
+    cin >> n;
+    set<int> ones, others;
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+        if (a[i] == 1) ones.insert(i);
+        else others.insert(i);
+    }
+    while (true) {
+        int x;
+        cin >> x;
+        if (a[x] == 1) {
+            ones.erase(x);
+            cout << 1 << endl;
+            if (ones.size() == 0 && others.size() == 0)
+                return cout << -1 << endl, 0;
+            cout << *ones.begin() << endl;
+            ones.erase(ones.begin());
+            cin >> x;
+        } else {
+            others.erase(x);
+            if (others.size() == 0) {
+                cout << a[x] << endl;
+                if (ones.size() == 0)
+                    return cout << -1 << endl, 0;
+                cout << *ones.begin() << endl;
+                ones.erase(ones.begin());
+                cin >> x;
+            } else {
+                cout << a[x] - 1 << endl << x << endl;
+                cin >> x;
+            }
+        }
+    }
+    return 0;
+}