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refactor 95
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  • src/main/java/com/fishercoder/solutions

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+35
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src/main/java/com/fishercoder/solutions/_95.java

Lines changed: 35 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -5,55 +5,41 @@
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import java.util.ArrayList;
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import java.util.List;
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/**
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* 95. Unique Binary Search Trees II
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*
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* Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1...n.
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For example,
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Given n = 3, your program should return all 5 unique BST's shown below.
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1 3 3 2 1
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\ / / / \ \
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3 2 1 1 3 2
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/ / \ \
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2 1 2 3
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*/
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public class _95 {
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public static class Solution1 {
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public List<TreeNode> generateTrees(int n) {
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List<TreeNode> result = new ArrayList();
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if (n == 0) {
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return result;
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}
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return generateTrees(1, n);
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}
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private List<TreeNode> generateTrees(int start, int end) {
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List<TreeNode> result = new ArrayList();
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if (start > end) {
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result.add(null);
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return result;
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}
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if (start == end) {
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result.add(new TreeNode(start));
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return result;
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}
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for (int i = start; i <= end; i++) {
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List<TreeNode> leftList = generateTrees(start, i - 1);
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List<TreeNode> rightList = generateTrees(i + 1, end);
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for (TreeNode left : leftList) {
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for (TreeNode right : rightList) {
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TreeNode root = new TreeNode(i);
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root.left = left;
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root.right = right;
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result.add(root);
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}
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}
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}
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return result;
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}
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}
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public static class Solution1 {
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public List<TreeNode> generateTrees(int n) {
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List<TreeNode> result = new ArrayList();
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if (n == 0) {
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return result;
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}
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return generateTrees(1, n);
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}
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private List<TreeNode> generateTrees(int start, int end) {
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List<TreeNode> result = new ArrayList();
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if (start > end) {
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result.add(null);
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return result;
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}
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if (start == end) {
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result.add(new TreeNode(start));
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return result;
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}
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for (int i = start; i <= end; i++) {
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List<TreeNode> leftList = generateTrees(start, i - 1);
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List<TreeNode> rightList = generateTrees(i + 1, end);
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for (TreeNode left : leftList) {
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for (TreeNode right : rightList) {
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TreeNode root = new TreeNode(i);
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root.left = left;
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root.right = right;
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result.add(root);
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}
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}
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}
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return result;
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}
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}
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}

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