[gitsunmin] Week 13 Solutions

house-robber/gitsunmin.ts

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+/**
+ * https://leetcode.com/problems/house-robber/
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+
+function rob(nums: number[]): number {
+    const houseCount = nums.length;
+
+    if (houseCount === 0) return 0;
+    if (houseCount === 1) return nums[0];
+
+    const maxRobAmount = new Array(houseCount).fill(0);
+    maxRobAmount[0] = nums[0];
+    maxRobAmount[1] = Math.max(nums[0], nums[1]);
+
+    for (let i = 2; i < houseCount; i++) maxRobAmount[i] = Math.max(maxRobAmount[i - 1], maxRobAmount[i - 2] + nums[i]);
+
+    return maxRobAmount[houseCount - 1];
+};

lowest-common-ancestor-of-a-binary-search-tree/gitsunmin.ts

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+/**
+ * https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
+ * time complexity : O(log n)
+ * space complexity : O(1)
+ */
+
+class TreeNode {
+    val: number
+    left: TreeNode | null
+    right: TreeNode | null
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = (val === undefined ? 0 : val)
+        this.left = (left === undefined ? null : left)
+        this.right = (right === undefined ? null : right)
+    }
+}
+
+export function lowestCommonAncestor(root: TreeNode | null, p: TreeNode, q: TreeNode): TreeNode | null {
+    while (root) {
+        if (p.val < root.val && q.val < root.val) root = root.left;
+        else if (p.val > root.val && q.val > root.val) root = root.right;
+        else return root;
+    }
+    return null;
+};

meeting-rooms/gitsunmin.ts

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+/**
+ * https://www.lintcode.com/problem/920/
+ * time complexity : O(n log n)
+ * space complexity : O(log n)
+ */
+
+export class Interval {
+    start: number;
+    end: number;
+    constructor(start: number, end: number) {
+        this.start = start;
+        this.end = end;
+    }
+}
+g
+export function canAttendMeetings(intervals: Interval[]): boolean {
+    intervals.sort((a, b) => a.start - b.start);
+
+    for (let i = 0; i < intervals.length - 1; i++) {
+        const { end } = intervals[i];
+        const { start: nextStart } = intervals[i + 1];
+
+        if (end > nextStart) return false;
+    }
+    return true;
+}