剑指offer-问题6

阳光穿透心脏的1/2处 2022-05-10 13:03 198阅读 0赞

package offer;
    
    /**
     * offer interview 06
     */
    public class Test06 {
    
        public static class BinaryTreeNode{
            int value;
            BinaryTreeNode left;
            BinaryTreeNode right;
        }
    
        public static BinaryTreeNode construct(int[] preorder,int[] inorder){
            if (null == preorder || null == inorder || preorder.length != inorder.length || inorder.length < 1){
                return null;
            }
    
            return construct(preorder,0,preorder.length-1,inorder,0,inorder.length-1);
        }
    
        public static BinaryTreeNode construct(int[] preorder , int ps,int pe,int[] inorder ,int is, int ie ){
            if (ps > pe){
                return null;
            }
    
            //root
            int value = preorder[ps];
            int index = is;
    
            while (index <= ie && inorder[index] != value){
                index++;
            }
    
            if (index > ie){
                throw new RuntimeException("Invalid input");
            }
    
            BinaryTreeNode node = new BinaryTreeNode();
            node.value = value;
    
            node.left = construct(preorder,ps+1,ps +index - is,inorder,is,index-1);
            node.right = construct(preorder,ps + index -is +1 ,pe,inorder,index + 1,ie);
    
            return node;
        }
    
        public static void printTree(BinaryTreeNode root){
            if (null != root){
                printTree(root.left);
                System.out.print(root.value + " ");
                printTree(root.right);
            }
        }
    
        private static void test1(){
            int[] preorder = {1,2,4,7,3,5,6,8};
            int[] inorder = {4,7,2,1,5,3,8,6};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
        private static void test2(){
            int[] preorder = {1,2,3,4,5};
            int[] inorder = {5,4,3,2,1};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
        private static void test3(){
            int[] preorder = {1,2,3,4,5};
            int[] inorder = {1,2,3,4,5};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
    
        private static void test4(){
            int[] preorder = {1};
            int[] inorder = {1};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
        private static void test5(){
            int[] preorder = {1,2,4,5,3,6,7};
            int[] inorder = {4,2,5,1,6,3,7};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
        private static void test6(){
            construct(null,null);
        }
    
    
        private static void test7(){
            int[] preorder = {1,2,4,5,3,6,7};
            int[] inorder = {4,2,8,1,6,3,7};
            BinaryTreeNode root = construct(preorder,inorder);
            printTree(root);
        }
    
        public static void main(String[]  args){
            test1();
            System.out.println();
            test2();
            System.out.println();
            test3();
            System.out.println();
            test4();
            System.out.println();
            test5();
            System.out.println();
            test6();
            System.out.println();
            test7();
            System.out.println();
    
        }
    
    
    
    }