✅ (wip) P7911 莫名其妙不一样 https://www.luogu.com.cn/problem/P7911

second-large-number/data.in

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+100
+40 32 2 42 47 7 24 14 11 7 19 3 44 49 44 32 4 28 4 48 4 7 41 32 42 41 27 4 20 40 44 30 13 44 8 10 16 46 50 18 20 15 4 32 22 25 10 2 17 10 49 4 47 10 41 28 3 3 26 22 13 40 29 14 9 1 43 21 19 20 10 12 40 6 14 9 14 46 25 50 17 45 1 30 5 37 8 5 47 43 39 12 25 1 40 20 2 10 14 21 

second-large-number/main.cc

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+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+int main() {
+    int k;
+    cin >> k;
+    vector<int> arr;
+    for (int i = 0; i < k; i++) {
+        int t;
+        cin >> t;
+        arr.push_back(t);
+    }
+    auto ptr = unique(arr.begin(), arr.end());
+    arr.erase(ptr, arr.end());
+    if (arr.size() <= 2) {
+        cout << -1 << endl;
+        return 0;
+    }
+    sort(arr.begin(), arr.end());
+    arr.insert(arr.begin(), 1, 0);
+    auto kp = arr.size()-1;
+    cout << max(arr[kp - 2], arr[kp] % arr[kp - 1]) << endl;
+}