java - 我的递归程序没有按预期返回树中的最小元素

Question

我有一棵树，我正在尝试编写一个递归方法来查找树中的最小值，但是我的方法没有返回树中的最小元素，我运行程序时的输出是 Minimum 是: 24。这是我的代码:

package weekFour;

public class MinTree {

    static int min;

    static Tree tree = new Tree( 24, 
                 new Tree( 45, 
                     null , 
                     new Tree(8, null , null) ) , 
                 new Tree ( 17, 
                     new Tree (74 , null , null ) , 
                     null ) );

    public static void main(String[] args){
    MinTree mt = new MinTree();
    System.out.println("Minimum is: " + mt.findMin(tree, Integer.MAX_VALUE));
    }

    public int findMin(Tree tree, int min){

        if(tree.getVal() < min) {

            min = tree.getVal();
        }

        Tree tree1 = tree.left();
        if (tree1 != null) {
            findMin(tree1, min);
        }

        Tree tree2 = tree.right();
        if (tree2 != null) {
            findMin(tree2, min);
        }

        return min;
    }


}

class Tree {

   private int val;
   private Tree left, right;

   public Tree(int val, Tree left, Tree right){
     this.val = val;
     this.left = left;
     this.right = right;
   }

   public int getVal(){
      return val;
   }

   public Tree left(){
      return left;
   }

   public Tree right(){
      return right;
   }
}

谢谢你的时间

Answer 1

在您的 findMin 方法中，您没有捕获递归调用的结果...

改变:

Tree tree1 = tree.left();
if (tree1 != null) {
    findMin(tree1, min);
}

Tree tree2 = tree.right();
if (tree2 != null) {
    findMin(tree2, min);
}

像这样:

Tree tree1 = tree.left();
if (tree1 != null) {
    min = findMin(tree1, min);
}

Tree tree2 = tree.right();
if (tree2 != null) {
    min = findMin(tree2, min);
}