题解 | 标签在前K个近邻中的出现次数

#include <algorithm>
#include <climits>
#include <iostream>
#include <bits/stdc++.h>
#include <queue>
#include <vector>
using namespace std;

int main() {
    int k, m, n, s;
    cin >> k >> m >> n >> s;
    vector<vector<double>> samples(m + 1, vector<double>(n + 1));
    vector<vector<double>> fars(m, vector<double>(2));
    unordered_map<double, int> freq;
    for(int j = 0; j < n; j++) cin >> samples[0][j];
    for(int i = 1; i <= m; i++){
        double far = 0, diff;
        for(int j = 0; j < n; j++){
            cin >> samples[i][j];
            diff = samples[i][j] - samples[0][j];
            far += diff * diff;
        }
        cin >> samples[i][n];
        fars[i - 1] = {far, samples[i][n]}; 
    }
    sort(fars.begin(), fars.end());
    int maxFreq = INT_MIN, maxLabel;
    for(int i = 0; i < k; i++){
        double label = fars[i][1];
        freq[label]++;
    }
    for(auto it = freq.begin(); it != freq.end(); ++it){
        if(it->second > maxFreq){
            maxFreq = it->second;
        }
    }
    for(int i = 0; i < k; i++){
        if(freq[fars[i][1]] == maxFreq){
            maxLabel = fars[i][1];
            break;
        }
    }
    cout << maxLabel << " " << maxFreq << endl;
}
// 64 位输出请用 printf("%lld")