题解归档 - cf2219B2

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• 本地编号：cf2219B2
• 本地来源：problems/cf2219B2/idea.md
• 题目链接：https://codeforces.com/contest/2219/problem/B2
• 原始标题：cf2219B2 - Unique Values (Hard version)

思路

cf2219B2 - Unique Values (Hard version)

Pattern

The hard version only changes the original interactive query limit. In hacked
input, the entire array is provided, so B1 and B2 have the same offline
solution.

Store positions for each value and print the three positions of the unique
value whose list length is 3.

Checks

• python tools/math_reasoning_search.py --problem cf2219B2 -n 5 - required
  precheck done by plan flag.
• Local sample uses the hacked input format rather than the original transcript.

代码

来源：problems/cf2219B2/solution.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T;
    cin >> T;
    while (T--) {
        int n;
        cin >> n;
        vector<vector<int>> pos(n + 1);
        for (int i = 1; i <= 2 * n + 1; i++) {
            int x;
            cin >> x;
            pos[x].push_back(i);
        }
        for (int x = 1; x <= n; x++) {
            if ((int)pos[x].size() == 3) {
                cout << "! " << pos[x][0] << ' ' << pos[x][1] << ' ' << pos[x][2] << '\n';
                break;
            }
        }
    }
    return 0;
}