用C语言写出k最近邻分类算法实现代码

以下是用C语言实现k最近邻分类算法的示例代码：

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

typedef struct {
    double x;
    double y;
    int label;
} Point;

int main() {
    int k, n;
    printf("Enter the value of k: ");
    scanf("%d", &k);
    printf("Enter the number of points: ");
    scanf("%d", &n);

    Point* points = (Point*) malloc(n * sizeof(Point));

    printf("Enter the coordinates and label of each point:\n");
    for (int i = 0; i < n; i++) {
        scanf("%lf %lf %d", &points[i].x, &points[i].y, &points[i].label);
    }

    // Classify new points
    int q;
    printf("Enter the number of new points to classify: ");
    scanf("%d", &q);

    printf("Enter the coordinates of each new point:\n");
    for (int i = 0; i < q; i++) {
        double x, y;
        printf("Point %d: ", i+1);
        scanf("%lf %lf", &x, &y);

        // Compute distance between new point and all points in dataset
        double distances[n];
        for (int j = 0; j < n; j++) {
            double dx = x - points[j].x;
            double dy = y - points[j].y;
            distances[j] = sqrt(dx*dx + dy*dy);
        }

        // Find k nearest points
        int indices[n];
        for (int j = 0; j < n; j++) {
            indices[j] = j;
        }
        for (int j = 0; j < k; j++) {
            int min_index = j;
            for (int l = j+1; l < n; l++) {
                if (distances[l] < distances[min_index]) {
                    min_index = l;
                }
            }
            double temp_dist = distances[j];
            distances[j] = distances[min_index];
            distances[min_index] = temp_dist;
            int temp_index = indices[j];
            indices[j] = indices[min_index];
            indices[min_index] = temp_index;
        }

        // Classify new point by majority vote of k nearest points
        int label_counts[3] = {0, 0, 0};
        for (int j = 0; j < k; j++) {
            int label = points[indices[j]].label;
            label_counts[label-1]++;
        }
        int max_count = 0;
        int max_label = 1;
        for (int j = 0; j < 3; j++) {
            if (label_counts[j] > max_count) {
                max_count = label_counts[j];
                max_label = j+1;
            }
        }
        printf("Classified as label %d\n", max_label);
    }

    free(points);

    return 0;
}

这里实现了一个简单的k最近邻分类器，可以处理二维空间中的点，并将它们分为三个类别。用户可以输入要分类的新点的坐标，并得到它所属的类别。注意，这里假设数据集中有且仅有三个类别，因此在实际应用中可能需要根据具体情况作出调整。