[ganu] Week4

merge-two-sorted-lists/gwbaik9717.js

@@ -0,0 +1,46 @@
+// m: list1, n: list2
+// Time complexity: O(m+n)
+// Space complexity: O(m+n)
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} list1
+ * @param {ListNode} list2
+ * @return {ListNode}
+ */
+var mergeTwoLists = function (list1, list2) {
+  const answer = new ListNode();
+  let current = answer;
+
+  while (list1 && list2) {
+    if (list1.val < list2.val) {
+      current.next = new ListNode(list1.val);
+      list1 = list1.next;
+    } else {
+      current.next = new ListNode(list2.val);
+      list2 = list2.next;
+    }
+
+    current = current.next;
+  }
+
+  while (list1) {
+    current.next = new ListNode(list1.val);
+    list1 = list1.next;
+    current = current.next;
+  }
+
+  while (list2) {
+    current.next = new ListNode(list2.val);
+    list2 = list2.next;
+    current = current.next;
+  }
+
+  return answer.next;
+};

missing-number/gwbaik9717.js

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+// Time complexity: O(n)
+// Space complexity: O(1)
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var missingNumber = function (nums) {
+  const n = nums.length;
+  const target = (n * (n + 1)) / 2;
+
+  const sum = nums.reduce((a, c) => a + c, 0);
+
+  return target - sum;
+};

word-search/gwbaik9717.js

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+// h: height of the board, w: width of the board, n: length of the word
+// Time complexity: O(h * w * 4**n)
+// Space complexity: O(h * w + n)
+
+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ */
+var exist = function (board, word) {
+  const n = word.length;
+  const h = board.length;
+  const w = board[0].length;
+
+  const dy = [1, 0, -1, 0];
+  const dx = [0, 1, 0, -1];
+
+  const checked = Array.from({ length: h }, () =>
+    Array.from({ length: w }, () => 0)
+  );
+
+  let answer = false;
+
+  const dfs = (current, index) => {
+    if (index === n - 1) {
+      answer = true;
+      return;
+    }
+
+    const [cy, cx] = current;
+    checked[cy][cx] = 1;
+
+    for (let i = 0; i < dy.length; i++) {
+      const ny = cy + dy[i];
+      const nx = cx + dx[i];
+      const ni = index + 1;
+
+      if (
+        ny >= 0 &&
+        ny < h &&
+        nx >= 0 &&
+        nx < w &&
+        checked[ny][nx] === 0 &&
+        word[ni] === board[ny][nx]
+      ) {
+        dfs([ny, nx], ni);
+      }
+    }
+
+    checked[cy][cx] = 0;
+  };
+
+  for (let i = 0; i < h; i++) {
+    for (let j = 0; j < w; j++) {
+      if (board[i][j] === word[0] && !answer) {
+        dfs([i, j], 0);
+      }
+    }
+  }
+
+  return answer;
+};