大样本统计

/*
 * 思路：
 * 1. 使用IntStream来遍历count数组。
 * 2. 通过filter和summaryStatistics找到最小值、最大值和求和。
 * 3. 计算总和sum和总数totalCount，得出均值。
 * 4. 使用IntStream和Collectors来计算中位数和众数。
 */
import java.util.stream.IntStream;
import java.util.stream.Collectors;
import java.util.*;

public class Solution {
    public double[] sampleStats(int[] count) {
        int min = IntStream.range(0, count.length).filter(i -> count[i] > 0).findFirst().orElse(-1);
        int max = IntStream.range(0, count.length).filter(i -> count[i] > 0).reduce((a, b) -> b).orElse(-1);
        long totalCount = IntStream.of(count).sum();
        double mean = IntStream.range(0, count.length).mapToDouble(i -> i * count[i]).sum() / totalCount;
        int mode = IntStream.range(0, count.length).boxed().max(Comparator.comparingInt(i -> count[i])).orElse(-1);
        long mid = (totalCount + 1) / 2;
        long currCount = 0;
        double median = 0;
        List<Integer> list = IntStream.range(0, count.length).boxed().collect(Collectors.toList());
        for (int i : list) {
            currCount += count[i];
            if (currCount >= mid) {
                if (totalCount % 2 == 1) {
                    median = i;
                } else {
                    if (currCount == mid) {
                        for (int j = i + 1; j < count.length; j++) {
                            if (count[j] > 0) {
                                median = (i + j) / 2.0;
                                break;
                            }
                        }
                    } else {
                        median = i;
                    }
                }
                break;
            }
        }
        return new double[]{min, max, mean, median, mode};
    }
}