[soobing] WEEK 01 Solutions

best-time-to-buy-and-sell-stock/soobing.ts

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+function maxProfit(prices: number[]): number {
+  let minPrice = Infinity;
+  let maxProfit = 0;
+  for (let i = 0; i < prices.length; i++) {
+    if (prices[i] < minPrice) {
+      minPrice = prices[i];
+    }
+
+    if (prices[i] - minPrice > maxProfit) {
+      maxProfit = prices[i] - minPrice;
+    }
+  }
+  return maxProfit;
+}

contains-duplicate/soobing.ts

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+function containsDuplicate(nums: number[]): boolean {
+  const map = new Map();
+  for (let i = 0; i < nums.length; i++) {
+    if (map.get(nums[i])) {
+      return true;
+    } else map.set(nums[i], 1);
+  }
+
+  return false;
+}

maximum-subarray/soobing.ts

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+function maxSubArray(nums: number[]): number {
+  let currentSum = nums[0];
+  let maxSum = nums[0];
+  for (let i = 1; i < nums.length; i++) {
+    currentSum = Math.max(nums[i], currentSum + nums[i]);
+    maxSum = Math.max(maxSum, currentSum);
+  }
+  return maxSum;
+}

product-of-array-except-self/soobing.ts

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+function productExceptSelf(nums: number[]): number[] {
+  const left = Array(nums.length).fill(1);
+  const right = Array(nums.length).fill(1);
+  const result = Array(nums.length);
+
+  for (let i = 1; i < nums.length; i++) {
+    left[i] = left[i - 1] * nums[i - 1];
+  }
+
+  for (let i = nums.length - 2; i >= 0; i--) {
+    right[i] = right[i + 1] * nums[i + 1];
+  }
+
+  for (let i = 0; i < nums.length; i++) {
+    result[i] = left[i] * right[i];
+  }
+
+  return result;
+}

two-sum/soobing.ts

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+// 1. Brute force
+function twoSum(nums: number[], target: number): number[] {
+  for (let i = 0; i < nums.length - 1; i++) {
+    for (let j = i + 1; j < nums.length; j++) {
+      if (nums[i] + nums[j] === target) {
+        return [i, j];
+      }
+    }
+  }
+  return [];
+}
+
+// 2. Hashmap
+function twoSum(nums: number[], target: number): number[] {
+  const map = new Map();
+  for (let i = 0; i < nums.length; i++) {
+    map.set(nums[i], i);
+  }
+
+  for (let i = 0; i < nums.length; i++) {
+    const targetIndex = map.get(target - nums[i]);
+    if (targetIndex && targetIndex !== i) {
+      return [i, targetIndex];
+    }
+  }
+  return [];
+}