EASY/src/easy/ClosestBinarySearchTreeValue.java

fishercoder1534 · fishercoder1534 · commit 926b9e257f44 · 2016-08-30T12:24:06.000-07:00
diff --git a/EASY/src/easy/ClosestBinarySearchTreeValue.java b/EASY/src/easy/ClosestBinarySearchTreeValue.java
@@ -0,0 +1,84 @@
+package easy;
+
+import classes.TreeNode;
+
+public class ClosestBinarySearchTreeValue {
+    
+    class General_tree_solution {
+        //this finished in 1 ms
+        public int closestValue(TreeNode root, double target) {
+            if (root == null)
+                return 0;
+            double delta = Double.MAX_VALUE;
+            return dfs(root, target, delta, root.val);
+        }
+
+        private int dfs(TreeNode root, double target, double delta, int closestVal) {
+            if (Math.abs(root.val - target) < delta) {
+                closestVal = root.val;
+                delta = Math.abs(root.val - target);
+            }
+            int leftVal = closestVal;
+            if (root.left != null)
+                leftVal = dfs(root.left, target, delta, closestVal);
+            int rightVal = closestVal;
+            if (root.right != null)
+                rightVal = dfs(root.right, target, delta, closestVal);
+            return (Math.abs(leftVal - target) > Math.abs(rightVal - target)) ? rightVal : leftVal;
+        }
+    }
+    
+    class BST_solution_recursive{
+        //we can tailor the solution to use the BST feature: left subtrees are always smaller than the root the right subtrees
+        //this finished in 0 ms
+        public int closestValue(TreeNode root, double target) {
+            if(root == null) return 0;
+            return dfs(root, target, root.val);
+        }
+
+        private int dfs(TreeNode root, double target, int minVal) {
+            if(root == null) return minVal;
+            if(Math.abs(root.val - target) < Math.abs(minVal - target)){
+                minVal = root.val;
+            }
+            if(target < root.val){
+                minVal = dfs(root.left, target, minVal);
+            } else {
+                minVal = dfs(root.right, target, minVal);
+            }
+            return minVal;
+        }
+    }
+    
+    class General_tree_solution_more_concise{
+        public int closestValue(TreeNode root, double target) {
+            if(root == null) return 0;
+            return dfs(root, target, root.val);
+        }
+
+        private int dfs(TreeNode root, double target, int minVal) {
+            if (root == null)
+                return minVal;
+            if (Math.abs(root.val - target) < Math.abs(minVal - target)) {
+                minVal = root.val;
+            }
+            minVal = dfs(root.left, target, minVal);
+            minVal = dfs(root.right, target, minVal);
+            return minVal;
+        }
+    }
+    
+    class BST_solution_iterative{
+        public int closestValue(TreeNode root, double target) {
+            long minVal = Long.MAX_VALUE;
+            while(root != null){
+                if(Math.abs(root.val - target) < Math.abs(minVal - target)){
+                    minVal = root.val;
+                }
+                if(target < root.val) root = root.left;
+                else root = root.right;
+            }
+            return minVal == Long.MAX_VALUE ? 0 : (int) minVal;
+        }
+    }
+}
