[yhkee0404] WEEK 15 solutions

alien-dictionary/yhkee0404.kt

@@ -0,0 +1,63 @@
+class Solution {
+    /**
+     * @param words: a list of words
+     * @return: a string which is correct order
+     */
+    fun alienOrder(words: Array<String>): String {
+        // Write your code here
+        val adj = List<MutableList<Int>>('z'.code - 'a'.code + 1) {mutableListOf()}
+        for (i in 1 until words.size) {
+            var j = 0
+            while (j != words[i - 1].length && j != words[i].length && words[i - 1][j] == words[i][j]) {
+                j++
+            }
+            if (j == words[i - 1].length) {
+                continue
+            }
+            if (j == words[i].length) {
+                return ""
+            }
+            adj[words[i - 1][j].code - 'a'.code].add(words[i][j].code - 'a'.code)
+        }
+        val visited = MutableList(adj.size) {false}
+        words.forEach {
+                    it.map { it.code - 'a'.code }
+                            .forEach { visited[it] = true }
+                }
+        val inDegrees = MutableList(adj.size) {0} // Kahn T(V, E) = S(V, E) = O(V + E)
+        adj.forEach {
+                    it.forEach { inDegrees[it]++ }
+                }
+        val ans = mutableListOf<Int>()
+        val stack = mutableListOf<Int>()
+        (0 until adj.size).filter { visited[it] && inDegrees[it] == 0 }
+                .forEach {
+                    stack.add(it)
+                    ans.add(it)
+                }
+        while (! stack.isEmpty()) {
+            val u = stack.removeLast()
+            adj[u].forEach {
+                        if (--inDegrees[it] == 0) {
+                            stack.add(it)
+                            ans.add(it)
+                        }
+                    }
+        }
+        if ((0 until adj.size).any { visited[it] && inDegrees[it] != 0 }) {
+            return ""
+        }
+        return ans.map { (it + 'a'.code).toChar() }
+                .joinToString("")
+        /*val decoder = MutableList(adj.size) {0}
+        (0 until ans.size).forEach { decoder[ans[it]] = it }
+        val decoded = words.map {
+                    it.map { (decoder[it.code - 'a'.code] + 'a'.code).toChar() }
+                            .joinToString("")
+                }
+        val sortedWords = decoded.sorted()
+        return if (decoded == sortedWords) ans.map { (it + 'a'.code).toChar() }
+                        .joinToString("")
+            else ""*/
+    }
+}

construct-binary-tree-from-preorder-and-inorder-traversal/yhkee0404.dart

@@ -0,0 +1,31 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *   int val;
+ *   TreeNode? left;
+ *   TreeNode? right;
+ *   TreeNode([this.val = 0, this.left, this.right]);
+ * }
+ */
+class Solution {
+  TreeNode? buildTree(List<int> preorder, List<int> inorder) {
+    int i = 1, j = 0;
+    final root = TreeNode(preorder[0]);
+    final stack = [root]; // T(n) = S(n) = O(n)
+    while (i != preorder.length) {
+        var u = stack.last;
+        if (u.val != inorder[j]) {
+            u.left = TreeNode(preorder[i++]);
+            stack.add(u.left!);
+            continue;
+        }
+        while (! stack.isEmpty && stack.last.val == inorder[j]) {
+            u = stack.removeLast();
+            j++;
+        }
+        u.right = TreeNode(preorder[i++]);
+        stack.add(u.right!);
+    }
+    return root;
+  }
+}

longest-palindromic-substring/yhkee0404.scala

@@ -0,0 +1,44 @@
+import scala.collection.mutable.ArrayBuffer
+
+object Solution {
+    def longestPalindrome(s: String): String = {
+        val list = ArrayBuffer[Char]()
+        for (c <- s) {
+            list += c
+            list += '\u0000'
+        }
+        val dp = Array.fill(list.size - 1)(0)
+        var lastR = -1
+        var lastMid = -1
+        var maxD = 0
+        var ansL = 0
+        var ansR = 0
+        var i = 1
+        for (i <- 0 until dp.size) { // Manacher T(n) = S(n) = O(n)
+            val diff = lastR - i
+            var d = if (diff <= 0) 0 else diff min dp((lastMid << 1) - i)
+            var l = i - d
+            var r = i + d
+            while (l != 0 && r != list.size - 1 && list(l - 1) == list(r + 1)) {
+                d += 1
+                l -= 1
+                r += 1
+            }
+            if (maxD < d) {
+                maxD = d
+                ansL = l
+                ansR = r
+            }
+            dp(i) = d
+            if (lastR < r) {
+                lastR = r
+                lastMid = i
+            }
+        }
+        val sb = StringBuilder()
+        for (i <- ansL to ansR if list(i) != '\u0000') {
+            sb.append(list(i))
+        }
+        sb.toString
+    }
+}

rotate-image/yhkee0404.go

@@ -0,0 +1,14 @@
+func rotate(matrix [][]int)  {
+    for i := range len(matrix) {
+        for j := i + 1; j != len(matrix[i]); j++ { // T(n) = O(n)
+            matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
+        }
+    }
+    for _, row := range matrix {
+        for i, j := 0, len(row) - 1; i < j; {
+            row[i], row[j] = row[j], row[i]
+            i++
+            j--
+        } 
+    }
+}

subtree-of-another-tree/yhkee0404.rs

@@ -0,0 +1,56 @@
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+// 
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    pub fn is_subtree(root: Option<Rc<RefCell<TreeNode>>>, sub_root: Option<Rc<RefCell<TreeNode>>>) -> bool {
+        match &root {
+            Some(u) => {
+                let u = u.borrow();
+                match &sub_root {
+                    Some(v) => {
+                        let v = v.borrow();
+                        Self::solve(root.clone(), sub_root.clone())
+                                || Self::is_subtree(u.left.clone(), sub_root.clone())
+                                || Self::is_subtree(u.right.clone(), sub_root.clone())
+                    },
+                    None => false,
+                }
+            },
+            None => sub_root.is_none(),
+        }
+    }
+    fn solve(root: Option<Rc<RefCell<TreeNode>>>, sub_root: Option<Rc<RefCell<TreeNode>>>) -> bool {
+        match root {
+            Some(u) => {
+                let u = u.borrow();
+                match &sub_root {
+                    Some(v) => {
+                        let v = v.borrow();
+                        u.val == v.val
+                                && Self::solve(u.left.clone(), v.left.clone())
+                                && Self::solve(u.right.clone(), v.right.clone())
+                    },
+                    None => false,
+                }
+            },
+            None => sub_root.is_none(),
+        }
+    }
+}