LESSON 49 / 75·2 min readFoundation

Arrays and strings in C#

Should knowConcept lesson

Problems to practice

Two Sum
Best Time to Buy and Sell Stock
Move Zeroes
Product of Array Except Self
Valid Palindrome
Longest Substring Without Repeating Characters
Group Anagrams

Example: two sum

public int[] TwoSum(int[] nums, int target) {
    var map = new Dictionary<int, int>();

    for (int i = 0; i < nums.Length; i++) {
        int needed = target - nums[i];
        if (map.ContainsKey(needed)) {
            return new[] { map[needed], i };
        }
        map[nums[i]] = i;
    }

    return Array.Empty<int>();
}