问题描述:
BST树,又称二叉查找树,求其到所有叶子节点路径的最小值
测试用例一: 10
5 20
返回15;
测试用例二: 100
20 70 110 120
10 null null 89 null null null null
返回130;
程序代码实现:
1 package examination.written; 2 3 /** 4 * 5 * @author ZhuXY 6 * @time 2016-6-12 下午9:57:53 7 * 8 */ 9 public class BSTMinLength { 10 11 public static void main(String[] args) { 12 13 /* 14 * root: tNodeRoot 15 * one layer: tNode21 tNode22 16 * two layer:tNode11 tNode12 tNode13 tNode14 17 */ 18 19 //构造一个BST树 20 TreeNode tNode11 = new TreeNode(10, null, null); 21 TreeNode tNode12 = new TreeNode(50, null, null); 22 TreeNode tNode13 = new TreeNode(5, null, null); 23 TreeNode tNode14 = new TreeNode(30, null, null); 24 25 TreeNode tNode21 = new TreeNode(30, tNode11, tNode12); 26 TreeNode tNode22 = new TreeNode(30, tNode13, tNode14); 27 28 TreeNode tNodeRoot = new TreeNode(100, tNode21, tNode22); 29 30 System.out.println(minlength(tNodeRoot)); 31 32 } 33 34 /** 35 * 获取BST树的最短路径 36 * @param tNode 37 * @return minLength:BST最短路径 38 */ 39 private static int minlength(TreeNode tNode) { 40 // TODO Auto-generated method stub 41 if (tNode != null) { 42 return getlength(tNode,0); 43 } 44 return -1; 45 } 46 47 /** 48 * 递归获取非空根节点到叶子节点的最短路径 49 * @param tNode 50 * @param curLength 51 * @return minLeft>minRight? minRight:minLeft 52 */ 53 private static int getlength(TreeNode tNode,int curLength) { 54 // TODO Auto-generated method stub 55 int minLeft=-1; 56 int minRight=-1; 57 58 // 左子树 59 if (tNode.leftNode!=null){ 60 minLeft=getlength(tNode.leftNode, curLength+tNode.value); 61 } 62 63 // 右子树 64 if (tNode.rightNode!=null) { 65 minRight=getlength(tNode.rightNode, curLength+tNode.value); 66 } 67 68 // 叶子节点 69 if (tNode.leftNode==null && tNode.rightNode==null) { 70 return curLength+tNode.value; 71 } 72 73 // 如果左子树为空 74 if (tNode.leftNode==null) { 75 return minRight; 76 } 77 78 // 如果右子树为空 79 if (tNode.rightNode==null) { 80 return minLeft; 81 } 82 83 // 如果右子树和左子树都不为空 84 return minLeft>minRight? minRight:minLeft; 85 } 86 } 87 88 /** 89 * 定义BST树结构类型 90 * @author ZhuXY 91 * 92 */ 93 class TreeNode { 94 int value; 95 TreeNode leftNode; 96 TreeNode rightNode; 97 98 TreeNode(int value, TreeNode lefeNode, TreeNode rightNode) { 99 this.value = value; 100 this.leftNode = lefeNode; 101 this.rightNode = rightNode; 102 } 103 }