[jjipper] WEEK 01 solutions

contains-duplicate/jjipper.ts

@@ -0,0 +1,16 @@
+/**
+ * https://leetcode.com/problems/contains-duplicate
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+
+export function containsDuplicate(nums: number[]): boolean {
+    const seen = new Set<number>();
+    for (const num of nums) {
+        if (seen.has(num)) {
+            return true;
+        }
+        seen.add(num);
+    }
+    return false;
+};

two-sum/jjipper.ts

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+/**
+ * https://leetcode.com/problems/two-sum
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+
+export function twoSum(nums: number[], target: number): number[] {
+    const obj: Record<number, number> = {};
+    for (let i = 0; i < nums.length; i++) {
+        const a = nums[i];
+        const b = target - a;
+        if (b in obj) {
+            return [obj[b], i];
+        }
+        obj[a] = i;
+    }
+    return [];
+};