數據挖掘-knn

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
struct node {
	int id;
	double x, y;
}a[N], b[N], t;
int len, k;
int n;
double distance(node x, node y) {
	return sqrt((x.x - y.x) * (x.x - y.x) + (x.y - y.y) * (x.y - y.y));
}
int main() {
	scanf("%d", &n);
	for(int i = 1; i <= n; i++) scanf("%lf %lf", &a[i].x, &a[i].y), a[i].id = i;
	len = 0;
	scanf("%d", &k);
	scanf("%lf %lf", &t.x, &t.y);
	double cnt, minn, tmp;
	int id;
	for(int i = 1; i <= n; i++) {
		if(i <= k) {
			b[i] = a[i];
		} else {
			cnt = distance(t, a[i]);	
			minn = 0;
			for(int j = 1; j <= k; j++) {
				tmp = distance(t, b[j]);
				if(tmp > minn) {
					id = j;
					minn = tmp;
				}
			}
			if(minn > cnt) {
				b[id] = a[i];
			}
		}
	}
	for(int i = 1; i <= k; i++)
		printf("%d %lf %lf\n", b[i].id, b[i].x, b[i].y);
	return 0;
}