交作业
Topic source这个地方有点问题,最后 应该为 `orElse(end)`
package com.github.hcsp.sql;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Created by chengww on 2019/10/10.
*/
public class Main {
public static void main(String[] args) {
// 构造从start到end的序列:
final int start = 10;
final int end = 20;
List<Integer> list = new ArrayList<>();
for (int i = start; i <= end; i++) {
list.add(i);
}
// 洗牌算法 shuffle 可以随机交换List中的元素位置:
Collections.shuffle(list);
// 随机删除List中的一个元素:
int removed = list.remove((int) (Math.random() * list.size()));
int found = findMissingNumber(start, end, list);
System.out.println(list.toString());
System.out.println("missing number: " + found);
System.out.println(removed == found ? "测试成功" : "测试失败");
}
static int findMissingNumber(int start, int end, List<Integer> list) {
list.sort(Comparator.comparingInt(e -> e));
return list.stream().filter(element -> start + list.indexOf(element) != element)
.findFirst().map(integer -> integer - 1).orElse(end);
}
}
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