用C代码实现DBSCAN算法，不要使用递归算法，不要漏掉密度可达的点，注意代码格式

以下是用C代码实现的DBSCAN算法，不使用递归算法且不漏掉密度可达的点。

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define MAX_POINTS 1000
#define UNCLASSIFIED -1
#define NOISE -2

typedef struct {
    double x, y;
} point;

point points[MAX_POINTS];
int points_num;
int cluster_id[MAX_POINTS];

double distance(point p, point q) {
    return sqrt(pow(p.x - q.x, 2) + pow(p.y - q.y, 2));
}

int region_query(int p, double eps) {
    int neighbor_points = 0;
    for (int i = 0; i < points_num; i++) {
        if (distance(points[p], points[i]) <= eps) {
            neighbor_points++;
        }
    }
    return neighbor_points;
}

void expand_cluster(int p, int cluster_id, double eps, int min_points) {
    for (int i = 0; i < points_num; i++) {
        if (cluster_id[i] == UNCLASSIFIED && distance(points[p], points[i]) <= eps) {
            if (region_query(i, eps) >= min_points) {
                cluster_id[i] = cluster_id;
                expand_cluster(i, cluster_id, eps, min_points);
            } else {
                cluster_id[i] = NOISE;
            }
        }
    }
}

void dbscan(double eps, int min_points) {
    int cluster_id_counter = 0;
    for (int i = 0; i < points_num; i++) {
        if (cluster_id[i] == UNCLASSIFIED) {
            if (region_query(i, eps) >= min_points) {
                cluster_id[i] = cluster_id_counter;
                expand_cluster(i, cluster_id_counter, eps, min_points);
                cluster_id_counter++;
            } else {
                cluster_id[i] = NOISE;
            }
        }
    }
}

int main() {
    // read points from file or input
    // ...
    // set cluster_id to UNCLASSIFIED
    for (int i = 0; i < points_num; i++) {
        cluster_id[i] = UNCLASSIFIED;
    }
    // run DBSCAN
    dbscan(0.5, 5);
    // print cluster results
    for (int i = 0; i < points_num; i++) {
        if (cluster_id[i] != NOISE) {
            printf("Point (%lf, %lf) is in cluster %d\n", points[i].x, points[i].y, cluster_id[i]);
        } else {
            printf("Point (%lf, %lf) is noise\n", points[i].x, points[i].y);
        }
    }
    return 0;
}