[hyer0705] WEEK 01 solutions

contains-duplicate/hyer0705.ts

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+function containsDuplicate(nums: number[]): boolean {
+  return new Set<number>(nums).size !== nums.length;
+}

house-robber/hyer0705.ts

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+// 0ms
+function rob(nums: number[]): number {
+  const n = nums.length;
+
+  if (n === 1) return nums[0];
+  if (n === 2) return Math.max(nums[0], nums[1]);
+
+  const dp: number[] = Array(n).fill(0);
+  dp[0] = nums[0];
+  dp[1] = Math.max(nums[0], nums[1]);
+
+  for (let i = 2; i < n; i++) {
+    dp[i] = Math.max(dp[i - 2] + nums[i], dp[i - 1]);
+  }
+
+  return dp[n - 1];
+}
+
+// 1ms
+/*
+function rob(nums: number[]): number {
+  const n = nums.length;
+
+  const dp: number[][] = Array.from({ length: n }, () => Array(2).fill(0));
+
+  dp[0][1] = nums[0];
+
+  for (let i = 1; i < n; i++) {
+    dp[i][0] = Math.max(dp[i - 1][0], dp[i - 1][1]);
+    dp[i][1] = dp[i - 1][0] + nums[i];
+  }
+
+  return Math.max(...dp[n - 1]);
+}
+*/

longest-consecutive-sequence/hyer0705.ts

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+function longestConsecutive(nums: number[]): number {
+  if (nums.length === 0) return 0;
+
+  const numSet = new Set<number>(nums);
+  let longest = 0;
+
+  for (const num of numSet) {
+    if (!numSet.has(num - 1)) {
+      let currentNum = num;
+      let sequenceLength = 1;
+
+      while (numSet.has(currentNum + 1)) {
+        currentNum++;
+        sequenceLength++;
+      }
+
+      longest = Math.max(longest, sequenceLength);
+    }
+  }
+
+  return longest;
+}

top-k-frequent-elements/hyer0705.ts

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+function topKFrequent(nums: number[], k: number): number[] {
+  nums.sort((a, b) => a - b);
+
+  const countMap = new Map<number, number>();
+
+  let pointer = 0;
+  while (pointer < nums.length) {
+    const currentNumber = nums[pointer];
+    let count = 0;
+
+    while (nums[pointer] === currentNumber) {
+      pointer++;
+      count++;
+    }
+
+    countMap.set(currentNumber, count);
+  }
+
+  const result = Array.from(countMap)
+    .sort((a, b) => b[1] - a[1])
+    .slice(0, k)
+    .map((value) => value[0]);
+
+  return result;
+}

two-sum/hyer0705.ts

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+function twoSum(nums: number[], target: number): number[] {
+  const numsLen = nums.length;
+  const result: number[] = [];
+
+  for (let i = 0; i < numsLen - 1; i++) {
+    for (let j = i + 1; j < numsLen; j++) {
+      if (nums[i] + nums[j] === target) {
+        result.push(i);
+        result.push(j);
+        break;
+      }
+    }
+  }
+
+  return result;
+}