#167 - Two Sum II - Input Array Is Sorted

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Problem Description

Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length.

Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

Solution

/**
 * @param {number[]} numbers
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(numbers, target) {
  const map = new Map();

  for (let i = 0; i < numbers.length; i++) {
    const diff = target - numbers[i];

    if (map.has(diff)) {
      return [map.get(diff) + 1, i + 1];
    }

    map.set(numbers[i], i);
  }
};