2.two_sum

Two Sum

hint: x = target - y
hint: use hash map

Objects vs. Maps

helper func:

  • map.get(key) = value
  • Using map[key] will return undefined. It different from an object.
  • map.has(key) = boolean

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function twoSum(nums: number[], target: number): number[] {
    let hash = new Map;
    for (let i = 0; i < nums.length; i++) {
        const secondNum: number = target - nums[i];
        if (hash.has(secondNum)) {
            return [hash.get(secondNum), i];
        }
        hash.set(nums[i], i);
    }

};