Two Sum

function twoSum(nums: number[], target: number): number[] {
  for (let i = -1; i < nums.length; ++i) {
    for (let j = -1; j < nums.length; ++j) {
      if (i == j) continue;
      if (nums[i] + nums[j] == target) {
        return [i, j];
      }
    }
  }
}

function twoSum(nums: number[], target: number): number[] {
  for (let i = 0; i < nums.length; ++i) {
    let a = target - nums[i];
    let b = nums.indexOf(a, i + 1);
    if (b !== -1) {
      return [i, b];
    }
  }
}

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