[yoonthecoder] Week 5

3sum/yoonthecoder.js

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+var threeSum = function (nums) {
+  nums.sort((a, b) => a - b);
+  const results = [];
+  for (let i = 0; i < nums.length - 2; i++) {
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+    let left = i + 1;
+    let right = nums.length - 1;
+    while (left < right) {
+      const currSum = nums[i] + nums[left] + nums[right];
+
+      if (currSum == 0) {
+        results.push([nums[i], nums[left], nums[right]]);
+        left++;
+        right--;
+        // to avoid duplicates
+        while (left < right && nums[left] === nums[left - 1]) left++;
+        while (left < right && nums[right] === nums[right + 1]) right--;
+      } else if (currSum < 0) {
+        left++;
+      } else right--;
+    }
+  }
+  return results;
+};
+
+// Time complexity: O(n^2);
+// Space complexity: O(n)

best-time-to-buy-and-sell-stock/yoonthecoder.js

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+var maxProfit = function (prices) {
+  // set the initial value to Infinity so that it can always return minimum value
+  let minPrice = Infinity;
+  let maxPrice = 0;
+  for (i = 0; i < prices.length; i++) {
+    minPrice = Math.min(prices[i], minPrice);
+    maxPrice = Math.max(maxPrice, prices[i + 1] - minPrice);
+  }
+  return maxPrice;
+};
+
+// Time complexity: O(n) - Iterating through the array
+// Space complexity: O(1)

group-anagrams/yoonthecoder.js

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+var groupAnagrams = function (strs) {
+  const map = new Map();
+
+  for (const str of strs) {
+    // split the string into each character (returns an array) => sort it => convert it to string
+    const sortedStr = str.split('').sort().join('');
+    // use the sorted Str as unique keys in the map
+    if (map.has(sortedStr)) {
+      map.get(sortedStr).push(str);
+    } else map.set(sortedStr, [str]);
+  }
+  // convert values into an array
+  return [...map.values()];
+};