根据列表的值将列表排序为多个列表

Question

List<Integer> = [1,2,3,4,8,7,5,6]

List<List<Integer>> = [[1,2,3,4,8], [8,7,5], [5,6]]

List<Integer> = [8,7,8,9]

List<List<Integer>> = [[8,7], [7,8,9]]

List<Integer> = [1,2,2,1]

List<List<Integer>> = [[1,2], [2,2], [2,1]]

Answer 1

这里有些东西可能会有帮助。在重要的地方增加了说明作为注释。

关键组件是简单的枚举方向。除了“上升”和“下降”之外，我还假定了“平等”。如果不是必需的，则根据您的选择，在direction.asc或direction.desc中包含equals check。

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.BiPredicate;

public class SortedSubLists{
    public static void main( String[] args ){
        List<List<Integer>> testData = Arrays.asList( 
            Arrays.asList( 1,2,3,4,8,7,5,6 ),
            Arrays.asList( 8,7,8,9 ),
            Arrays.asList( 1,2,2,1 )
        );
        
        for( List<Integer> input : testData ) {
            List<List<Integer>> subLists = split( input );
            
            System.out.println( "\r\nInput: " + input );
            for( List<Integer> l : subLists ) System.out.println( l );
        }
    }

    /** Represents the direction of the movement of data */
    private static enum Direction {
        ASC(( prev, curr ) -> prev - curr < 0), DESC(( prev, curr ) -> prev - curr > 0), EQ(( prev, curr ) -> prev - curr == 0);

        private Direction( BiPredicate<Integer, Integer> applicability ){
            this.applicability = applicability;
        }

        private BiPredicate<Integer, Integer> applicability;

        static Direction get( Integer prev, Integer curr ){
            for( Direction d : values() ){
                if( d.applicability.test( prev, curr ) ) return d;
            }

            return null;
        }
    }

    private static List<List<Integer>> split( List<Integer> list ){
        Direction dir = null;
        List<List<Integer>> result = new ArrayList<>();

        Integer prev = null;
        List<Integer> currList = null;
        for( Integer i : list ){
            /* For the first element in the input, create a sub-list here and add the first element. */
            if( prev == null ) {
                currList = newList( result );
                currList.add( i );
            }
            else{
                /* Find the direction. If it has changed, create a new sub-list. Otherwise, continue with the
                 * existing one. */
                Direction newDir = Direction.get( prev, i );
                if( dir == null ) dir = newDir;
                else{
                    if( dir != newDir ) {
                        dir = newDir;
                        currList = newList( result );
                        currList.add( prev );
                    }
                }

                currList.add( i );
            }
            
            prev = i;

        }
        return result;
    }

    private static List<Integer> newList( List<List<Integer>> result ){
        List<Integer> newList = new ArrayList<>();
        result.add( newList );
        return newList;
    }
}

运行程序的输出

Input: [1, 2, 3, 4, 8, 7, 5, 6]
[1, 2, 3, 4, 8]
[8, 7, 5]
[5, 6]

Input: [8, 7, 8, 9]
[8, 7]
[7, 8, 9]

Input: [1, 2, 2, 1]
[1, 2]
[2, 2]
[2, 1]