[Yu-Won] WEEK 04 Solutions

coin-change/Yu-Won.js

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+/**
+ * @param {number[]} coins
+ * @param {number} amount
+ * @return {number}
+ *
+ * 문제: https://leetcode.com/problems/coin-change/
+ * 요구사항: 동전과 총 금액이 주어질 때 해당 금액을 만드는데 최소 동전 개수를 반환
+ */
+const coinChange = (coins, amount) => {
+    let dp = new Array(amount + 1).fill(amount + 1);
+    dp[0] = 0;
+    for (let i = 1; i <= amount; i++) {
+        for (const coin of coins) {
+            if (i - coin >= 0) {
+                dp[i] = Math.min(dp[i], dp[i - coin] + 1);
+            }
+        }
+    }
+
+    return dp[amount] > amount ? -1 : dp[amount];
+};

find-minimum-in-rotated-sorted-array/Yu-Won.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ *
+ * 문제: https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/
+ * 요구사항: 이진트리 활용
+ */
+const findMin = (nums) => {
+    let left = 0;
+    let right = nums.length - 1;
+
+    while (left < right) {
+        let mid = Math.floor((left + right) / 2);
+
+        if (nums[mid] > nums[right]) {
+            left = mid + 1;
+        } else {
+            right = mid;
+        }
+    }
+
+    return nums[left];
+};

maximum-depth-of-binary-tree/Yu-Won.js

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+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ *
+ * 문제: https://leetcode.com/problems/maximum-depth-of-binary-tree/
+ * 요구사항: 이진 트리의 최대 깊이를 반환하라.
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+const maxDepth = (root) => {
+    if(!root) return 0;
+
+    let queue = [root];
+    let depth = 0;
+
+    while(queue.length) {
+        let size = queue.length;
+
+        for(let i = 0; i < size; i++) {
+            let node = queue.shift();
+
+            if(node.left) queue.push(node.left);
+            if(node.right) queue.push(node.right);
+        }
+        depth++;
+    }
+    return depth;
+};

merge-two-sorted-lists/Yu-Won.js

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+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ *
+ * 문제: https://leetcode.com/problems/merge-two-sorted-lists/
+ * 요구사항: 정의된 ListNode 를 활용해서 정렬된 배열을 리턴
+ */
+/**
+ * @param {ListNode} list1
+ * @param {ListNode} list2
+ * @return {ListNode}
+ */
+
+
+const mergeTwoLists = (list1, list2) => {
+    const dummy = new ListNode(0);
+    let cur = dummy;
+
+    while (list1 && list2) {
+        if (list1.val <= list2.val) {
+            cur.next = list1;
+            list1 = list1.next;
+        } else {
+            cur.next = list2;
+            list2 = list2.next;
+        }
+        cur = cur.next;
+    }
+
+    cur.next = list1 ?? list2;
+    return dummy.next;
+};

word-search/Yu-Won.js

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+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ *
+ * 문제: https://leetcode.com/problems/word-search/
+ * 요구사항: 그리드 구조에서 word의 문자열 존재 여부에 따라 true/false를 리턴한다.
+ * 백트래킹, dfs
+ */
+const exist = (board, word) => {
+    let rows = board.length;
+    let cols = board[0].length;
+
+    const dfs = (r, c, index) => {
+        if (index === word.length) return true;
+
+        if (r < 0 || r >= rows || c < 0 || c >= cols || board[r][c] !== word[index]) {
+            return false;
+        }
+
+        let temp = board[r][c];
+        board[r][c] = '#';
+
+        let found = dfs(r + 1, c, index + 1) ||
+            dfs(r - 1, c, index + 1) ||
+            dfs(r, c + 1, index + 1) ||
+            dfs(r, c - 1, index + 1);
+
+        board[r][c] = temp;
+
+        return found;
+    }
+
+    for (let i = 0; i < rows; i++) {
+        for (let j = 0; j < cols; j++) {
+            if (board[i][j] === word[0] && dfs(i, j, 0)) return true;
+        }
+    }
+
+    return false;
+};