added task #783 solution. Explanations will be added later

Author: nesterrovv

src/task_783/Solution.java

@@ -0,0 +1,29 @@
+package task_783;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+
+public class Solution {
+
+    List<Integer> list = new ArrayList<>();
+
+    public int minDiffInBST(TreeNode root) {
+        searchValues(root);
+        int minDiff = 100001;
+        for (int i = 0; i < list.size() - 1; i++) {
+            minDiff = Math.min(minDiff, Math.abs(list.get(i) - list.get(i + 1)));
+        }
+        return minDiff;
+    }
+
+    private void searchValues(TreeNode root) {
+        if (root == null) {
+            return;
+        }
+        searchValues(root.left);
+        list.add(root.val);
+        searchValues(root.right);
+    }
+
+}

src/task_783/TreeNode.java

@@ -0,0 +1,22 @@
+package task_783;
+
+
+/** Definition for a binary tree node. */
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode() {
+    }
+
+    TreeNode(int val) {
+        this.val = val;
+    }
+
+    TreeNode(int val, TreeNode left, TreeNode right) {
+        this.val = val;
+        this.left = left;
+        this.right = right;
+    }
+}