[강희찬] WEEK 4 Solution

longest-consecutive-sequence/HC-kang.ts

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+/**
+ * https://leetcode.com/problems/longest-consecutive-sequence/
+ * T.C.: O(n)
+ * S.C.: O(n)
+ */
+function longestConsecutive(nums: number[]): number {
+  const numSet = new Set(nums);
+  let max = 0;
+
+  for (const num of numSet) {
+    if (numSet.has(num - 1)) {
+      continue;
+    }
+
+    let count = 0;
+    while (numSet.has(num + count)) {
+      count++;
+    }
+
+    if (count > max) max = count;
+  }
+
+  return max;
+}

maximum-product-subarray/HC-kang.ts

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+function maxProduct(nums: number[]): number {
+  return 0;
+}

missing-number/HC-kang.ts

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+/**
+ * https://leetcode.com/problems/missing-number/
+ * T.C.: O(n)
+ * S.C.: O(1)
+ */
+function missingNumber(nums: number[]): number {
+  let sum = nums.length; // i for 0 to n-1. So, n is missing.
+  for (let i = 0; i < nums.length; i++) sum = sum + i - nums[i];
+  return sum;
+}

valid-palindrome/HC-kang.ts

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+/**
+ * https://leetcode.com/problems/valid-palindrome/
+ * T.C.: O(n)
+ * S.C.: O(1)
+ */
+function isPalindrome(s: string): boolean {
+  function isAlNum(char: string): boolean {
+    return /^[a-zA-Z0-9]$/.test(char);
+  }
+
+  let left = 0;
+  let right = s.length - 1;
+  while (left < right) {
+    while (left < right && !isAlNum(s[left])) left++;
+    while (left < right && !isAlNum(s[right])) right--;
+
+    if (s[left].toLowerCase() !== s[right].toLowerCase()) {
+      return false;
+    }
+
+    left++;
+    right--;
+  }
+  return true;
+}

word-search/HC-kang.ts

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+function exist(board: string[][], word: string): boolean {
+  return false;
+}