我正在 Interviewbit 解决这个问题：
给定一组不同的整数S，返回所有可能的子集。子集中的元素必须是非降序。解决方案集不能包含重复的子集。
这是我的简单，自解释代码：
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javafx.animation.PathTransition;
import javafx.application.Application;
import javafx.geometry.Rectangle2D;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Pane;
import javafx.scene.shape.LineTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.stage.Stage;
import javafx.util.Duration;
public class PuzzleGame extends Application {
private Image image = new Image("http://images.cdn.autocar.co.uk/sites/autocar.co.uk/files/styles/gallery_slide/public/ferrari-laferrari-zfye-059_1.jpg?itok=hfLNxUD9",600,600,false,true);
private static double SCENE_WIDTH = 1024;
private static double SCENE_HEIGHT = 768;
public static int TILE_ROW_COUNT = 5;
public static int TILE_COLUMN_COUNT = 5;
public static double TILE_SIZE = 120;
public static double offsetX = (SCENE_WIDTH - TILE_ROW_COUNT * TILE_SIZE) / 2;
public static double offsetY = (SCENE_HEIGHT - TILE_COLUMN_COUNT * TILE_SIZE) / 2;
List<Cell> cells = new ArrayList<>();
@Override
public void start(Stage primaryStage) {
// create grid
for (int x = 0; x < TILE_ROW_COUNT; x++) {
for (int y = 0; y < TILE_COLUMN_COUNT; y++) {
// create tile
ImageView tile = new ImageView(image);
Rectangle2D rect = new Rectangle2D(TILE_SIZE * x, TILE_SIZE * y, TILE_SIZE, TILE_SIZE);
tile.setViewport(rect);
// consider empty cell, let it remain empty
if (x == (TILE_ROW_COUNT - 1) && y == (TILE_COLUMN_COUNT - 1)) {
tile = null;
}
cells.add(new Cell(x, y, tile));
}
}
// shuffle cells
shuffle();
// create playfield
Pane pane = new Pane();
// put tiles on playfield, assign event handler
for (int i = 0; i < cells.size(); i++) {
Cell cell = cells.get(i);
Node imageView = cell.getImageView();
// consider empty cell
if (imageView == null)
continue;
// click-handler: swap tiles, check if puzzle is solved
imageView.addEventFilter(MouseEvent.MOUSE_CLICKED, mouseEvent -> {
moveCell((Node) mouseEvent.getSource());
});
// position images on scene
imageView.relocate(cell.getLayoutX(), cell.getLayoutY());
pane.getChildren().add(cell.getImageView());
}
Scene scene = new Scene(pane, SCENE_WIDTH, SCENE_HEIGHT);
primaryStage.setScene(scene);
primaryStage.show();
}
/**
* Swap images of cells randomly
*/
public void shuffle() {
Random rnd = new Random();
for (int i = 0; i < 1000; i++) {
int a = rnd.nextInt(cells.size());
int b = rnd.nextInt(cells.size());
if (a == b)
continue;
// skip bottom right cell swap, we want the empty cell to remain there
if( cells.get(a).isEmpty() || cells.get(b).isEmpty())
continue;
swap( cells.get(a), cells.get(b));
}
}
public void swap( Cell cellA, Cell cellB) {
ImageView tmp = cellA.getImageView();
cellA.setImageView(cellB.getImageView());
cellB.setImageView(tmp);
}
public boolean checkSolved() {
boolean allSolved = true;
for (Cell cell : cells) {
if (!cell.isSolved()) {
allSolved = false;
break;
}
}
System.out.println("Solved: " + allSolved);
return allSolved;
}
public void moveCell(Node node) {
// get current cell using the selected node (imageview)
Cell currentCell = null;
for (Cell tmpCell : cells) {
if (tmpCell.getImageView() == node) {
currentCell = tmpCell;
break;
}
}
if (currentCell == null)
return;
// get empty cell
Cell emptyCell = null;
for (Cell tmpCell : cells) {
if (tmpCell.isEmpty()) {
emptyCell = tmpCell;
break;
}
}
if (emptyCell == null)
return;
// check if cells are swappable: neighbor distance either x or y must be 1 for a valid move
int steps = Math.abs(currentCell.x - emptyCell.x) + Math.abs(currentCell.y - emptyCell.y);
if (steps != 1)
return;
System.out.println("Transition: " + currentCell + " -> " + emptyCell);
// cells are swappable => create path transition
Path path = new Path();
path.getElements().add(new MoveToAbs(currentCell.getImageView(), currentCell.getLayoutX(), currentCell.getLayoutY()));
path.getElements().add(new LineToAbs(currentCell.getImageView(), emptyCell.getLayoutX(), emptyCell.getLayoutY()));
PathTransition pathTransition = new PathTransition();
pathTransition.setDuration(Duration.millis(100));
pathTransition.setNode(currentCell.getImageView());
pathTransition.setPath(path);
pathTransition.setOrientation(PathTransition.OrientationType.NONE);
pathTransition.setCycleCount(1);
pathTransition.setAutoReverse(false);
final Cell cellA = currentCell;
final Cell cellB = emptyCell;
pathTransition.setOnFinished(actionEvent -> {
swap( cellA, cellB);
checkSolved();
});
pathTransition.play();
}
private static class Cell {
int x;
int y;
ImageView initialImageView;
ImageView currentImageView;
public Cell(int x, int y, ImageView initialImageView) {
super();
this.x = x;
this.y = y;
this.initialImageView = initialImageView;
this.currentImageView = initialImageView;
}
public double getLayoutX() {
return x * TILE_SIZE + offsetX;
}
public double getLayoutY() {
return y * TILE_SIZE + offsetY;
}
public ImageView getImageView() {
return currentImageView;
}
public void setImageView(ImageView imageView) {
this.currentImageView = imageView;
}
public boolean isEmpty() {
return currentImageView == null;
}
public boolean isSolved() {
return this.initialImageView == currentImageView;
}
public String toString() {
return "[" + x + "," + y + "]";
}
}
// absolute (layoutX/Y) transitions using the pathtransition for MoveTo
public static class MoveToAbs extends MoveTo {
public MoveToAbs(Node node) {
super(node.getLayoutBounds().getWidth() / 2, node.getLayoutBounds().getHeight() / 2);
}
public MoveToAbs(Node node, double x, double y) {
super(x - node.getLayoutX() + node.getLayoutBounds().getWidth() / 2, y - node.getLayoutY() + node.getLayoutBounds().getHeight() / 2);
}
}
// absolute (layoutX/Y) transitions using the pathtransition for LineTo
public static class LineToAbs extends LineTo {
public LineToAbs(Node node, double x, double y) {
super(x - node.getLayoutX() + node.getLayoutBounds().getWidth() / 2, y - node.getLayoutY() + node.getLayoutBounds().getHeight() / 2);
}
}
public static void main(String[] args) {
launch(args);
}
}
这是输出：
ans_list=[]
def solve(i,a,tmp,l,k):
global ans_list
if i==l :
print "List to append: " ,tmp
ans_list.append(tmp)
print "ans_list currently: ", ans_list
return
j=k
while j < len(a):
tmp.append(a[j])
solve(i+1,a,tmp,l,j+1)
tmp.pop()
j+=1
class Solution:
# @param a : list of integers
# @return a list of list of integers
def subsets(self, a):
a=sorted(a)
global ans_list
tmp=[]
i=0
for l in range(len(a)+1):
solve(0,a,tmp,l,0)
return ans_list
def main():
a=[1,2,3]
ob=Solution()
li=ob.subsets(a)
print "Ans:" ,li
if __name__ == '__main__':
main()
我甚至尝试将List to append: []
Current ans_list: [[]]
List to append: [1]
Current ans_list: [[1], [1]]
List to append: [2]
Current ans_list: [[2], [2], [2]]
List to append: [3]
Current ans_list: [[3], [3], [3], [3]]
List to append: [1, 2]
Current ans_list: [[1, 2], [1, 2], [1, 2], [1, 2], [1, 2]]
List to append: [1, 3]
Current ans_list: [[1, 3], [1, 3], [1, 3], [1, 3], [1, 3], [1, 3]]
List to append: [2, 3]
Current ans_list: [[2, 3], [2, 3], [2, 3], [2, 3], [2, 3], [2, 3], [2, 3]]
List to append: [1, 2, 3]
Current ans_list: [[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]]
Ans: [[], [], [], [], [], [], [], []]
作为参数而不是全局变量传递，但结果是相同的。甚至尝试使用字典而不是列表列表，但它会导致相同的行为。然而，我注意到一件有趣的事情是当我在ans_list函数中将ans_list.append(tmp)更改为ans_list.extend(tmp)时输出变为：
solve这是非常期待的。现在我不确定在python中附加列表和字典会出现这种意外行为的原因是什么，而extend会给出正确的响应。任何帮助将不胜感激。
我是python的新手并使用Python 2.7.10
答案 0 :(得分：1)
问题是你在子集（）的循环外创建了 tmp 。现在 resolve（）中 tmp 的每次使用都将指向同一个列表，并且将对ans_list中的每个元素执行每个操作，包括pop（）。
有很多方法可以解决此问题，但如果您想要最少的代码更改，只需导入复制模块并更改：
ans_list.append(tmp)
为：
ans_list.append(copy.deepcopy(tmp))
编辑（我的解决方案）：
ans = set()
for i in range(len(a)+1):
for j in range(len(a)+1):
ans.add(tuple(a[i:j]))