1. Two Sum

two-sum.ts

Two Sum: 
https://leetcode.com/problems/two-sum/submissions/

// O(n^2)
for(let i = 0; i < array.length; i++) {
    for(let j = 1; j < array.length; j++) {
        if(array[i] + array[j] === target) {
            console.log('i: ' + i + ' j: ' + j);
        }
    }
}

// O(n)
function twoSum(nums: number[], target: number): number[] {
    const map: Map<number, number> = new Map();
    for (let i=0; i<nums.length; i++) {
        const current = nums[i];
        const remain = map.get(target - current);
        if (remain !== undefined) {
            return [i, remain];
        }
        map.set(current, i);
    }
    return [];
};

// [2,5,5,11]
// 10
// Input: nums = [2,7,11,15], target = 9
// Output: [0,1]

const array = [2,7,11,15];
// const array = [3,2,4];
// const array = [3,3];
// const array = [2,5,5,11];
const target = 9;
// const target = 6;
// const target = 10;

const answer = twoSum(array, target);
console.log(answer);