From 2d5cba6bb75fe7ecf4c9bd0d18b8364479cf8df6 Mon Sep 17 00:00:00 2001
From: HiGeuni <khyogeun_@naver.com>
Date: Sat, 4 Jan 2025 20:08:04 +0900
Subject: [PATCH] add: solution for week 4

---
 merge-two-sorted-lists/higeuni.js | 34 ++++++++++++++++++++++
 missing-number/higeuni.js         | 15 ++++++++++
 word-search/higeuni.js            | 47 +++++++++++++++++++++++++++++++
 3 files changed, 96 insertions(+)
 create mode 100644 merge-two-sorted-lists/higeuni.js
 create mode 100644 missing-number/higeuni.js
 create mode 100644 word-search/higeuni.js

diff --git a/merge-two-sorted-lists/higeuni.js b/merge-two-sorted-lists/higeuni.js
new file mode 100644
index 000000000..545a240f6
--- /dev/null
+++ b/merge-two-sorted-lists/higeuni.js
@@ -0,0 +1,34 @@
+/**
+ * @param {ListNode} list1
+ * @param {ListNode} list2
+ * @return {ListNode}
+ * 
+ * complexity
+ * time: O(n + m)
+ * space: O(1)
+ */
+
+var mergeTwoLists = function(list1, list2) {
+  let dummy = new ListNode();
+  let current = dummy;
+
+  while (list1 !== null && list2 !== null) {
+      if (list1.val < list2.val) {
+          current.next = list1;
+          list1 = list1.next;
+      } else {
+          current.next = list2;
+          list2 = list2.next;
+      }
+      current = current.next;
+  }
+
+  if (list1 !== null) {
+      current.next = list1;
+  } else if (list2 !== null) {
+      current.next = list2;
+  }
+
+  return dummy.next;
+};
+
diff --git a/missing-number/higeuni.js b/missing-number/higeuni.js
new file mode 100644
index 000000000..2a25ac51a
--- /dev/null
+++ b/missing-number/higeuni.js
@@ -0,0 +1,15 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ * 
+ * complexity
+ * time: O(n)
+ * space: O(1)
+ */
+
+var missingNumber = function(nums) {
+  const sumOfNums = nums.reduce((acc, curr) => acc + curr, 0);
+  const sumOfTotalNumbers = (nums.length * (nums.length + 1)) / 2;
+  return sumOfTotalNumbers - sumOfNums;
+};
+
diff --git a/word-search/higeuni.js b/word-search/higeuni.js
new file mode 100644
index 000000000..4e6fe19a2
--- /dev/null
+++ b/word-search/higeuni.js
@@ -0,0 +1,47 @@
+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ * 
+ * complexity
+ * time: O(n * m * 4^l)
+ * space: O(n * m)
+ */
+
+var exist = function(board, word) {
+  word = word.split('');
+  const dx = [-1, 1, 0, 0];
+  const dy = [0, 0, 1, -1];
+  const visited = Array.from({length: board.length}, () => Array(board[0].length).fill(false));
+
+  const dfs = (length, x, y) => {
+      if(word.length === length) {
+          return true;
+      }
+      for(let i = 0; i < 4; ++i) {
+          const nx = x + dx[i];
+          const ny = y + dy[i];
+          if(0 <= nx && nx < board[0].length && 0 <= ny && ny < board.length){
+              if(board[ny][nx] === word[length] && !visited[ny][nx]) {
+                  visited[ny][nx] = true;
+                  if(dfs(length + 1, nx, ny)) return true;
+                  visited[ny][nx] = false;
+              } 
+          }
+      }
+      return false;
+  }
+
+  for(let i = 0; i < board.length; ++i){
+      for(let j = 0; j < board[0].length; ++j){
+          if(board[i][j] === word[0]) {
+              visited[i][j] = true;
+              if(dfs(1, j, i)) return true;
+              visited[i][j] = false;
+          }
+      }
+  }
+
+  return false;
+};
+