[lhc0506] WEEK 1 solutions

contains-duplicate/lhc0506.js

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+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function(nums) {
+    const numsSet = new Set();
+    nums.forEach(num => numsSet.add(num));
+
+    return nums.length !== numsSet.size;
+};

house-robber/lhc0506.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var rob = function(nums) {
+    if (nums.length < 2) {
+        return Math.max(nums);
+    }
+
+    let twoBefore = 0;
+    let oneBefore = 0;
+
+    nums.forEach(num => {
+        const prevOneBefore = oneBefore;
+        oneBefore = Math.max(prevOneBefore, twoBefore + num);
+        twoBefore = prevOneBefore;
+    });
+
+    return Math.max(oneBefore, twoBefore);
+};

longest-consecutive-sequence/lhc0506.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+
+var longestConsecutive = function(nums) {
+    const numSet = new Set(nums);
+
+    let maxLength = 0;
+    let currentLength = 0;
+
+    const countConsecutive = (num, step) => {
+        let currentNum = num;
+        while(numSet.has(currentNum)) {
+            numSet.delete(currentNum);
+            currentNum += step;
+            currentLength += 1;
+        }
+    }
+
+    nums.forEach(num => {
+        countConsecutive(num, 1);
+        countConsecutive(num - 1, -1);
+
+        maxLength = Math.max(maxLength, currentLength);
+        currentLength = 0;
+    });
+
+    return maxLength;
+};

top-k-frequent-elements/lhc0506.js

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+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function(nums, k) {
+    const numsMap = {};
+
+    nums.forEach(num => {
+        numsMap[num] ? numsMap[num] += 1 : numsMap[num] = 1;
+    });
+
+    return Object.entries(numsMap).sort((a, b) => b[1] - a[1]).slice(0, k).map(([key]) => Number(key));
+};

two-sum/lhc0506.js

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+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function(nums, target) {
+    const numsMap = {};
+
+    for (let i = 0; i < nums.length; i++) {
+        const needNum = target - nums[i];
+
+        if (needNum in numsMap) {
+            return [i, numsMap[needNum]];
+        }
+
+        numsMap[nums[i]] = i;
+    }
+};