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# [twoSum](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted)
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## описание задачи
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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.
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Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.
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The tests are generated such that there is exactly one solution. You may not use the same element twice.
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Your solution must use only constant extra space.
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Example 1:
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- Input: numbers = [2,7,11,15], target = 9
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- Output: [1,2]
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- Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].
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Example 2:
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- Input: numbers = [2,3,4], target = 6
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- Output: [1,3]
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- Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].
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Example 3:
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- Input: numbers = [-1,0], target = -1
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- Output: [1,2]
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- Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].
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Constraints:
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2 <= numbers.length <= 3 * 104
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-1000 <= numbers[i] <= 1000
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numbers is sorted in non-decreasing order.
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-1000 <= target <= 1000
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The tests are generated such that there is exactly one solution.
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## тест кейсы
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```ts
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describe("twoSum", () => {
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it("[2,7,11,15] 9 => [1,2]", () => {
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expect(twoSum([2, 7, 11, 15], 9)).toEqual([1, 2]);
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});
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it("[2,3,4] 6 => [1,3]", () => {
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expect(twoSum([2, 3, 4], 6)).toEqual([1, 3]);
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});
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it("[-1, 0] -1 => [1, 2]", () => {
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expect(twoSum([-1, 0], -1)).toEqual([1, 2]);
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});
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it("[5,25,75] 100 => [2,3]", () => {
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expect(twoSum([5, 25, 75], 100)).toEqual([2, 3]);
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})
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});
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```
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## текстовое описание решения
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- заводим два указателя, в начале и конце
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- в цикле получаем по указателям значение и складываем
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- если сумма больше таргет двигаем правый указатель
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- если сумма меньше таргет двигаем левый указатель
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- если сумма равна таргет возвращаем значение указателей +1
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- если указатели сошлись а сумма не равна таргет выходим из цикла и возвращаем [-1, -1]
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## ассимптотическая оценка
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| Description | Estimation |
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| ----------- | ---------- |
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| time: | O(n) |
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| mem: | O(n) |
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## time
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| Description | Time |
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| ------------------------------------------- | ----- |
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| анализ и сбор информации | 11:50 |
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| обдумываение решения и формулировка решения | 08:47 |
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| имплементация | 20:28 |
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| исправление ошибок | 20:00 |
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| полное время затраченое на решение | 01:01:07 |
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## журнал ошибок
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- не разобрался с правилами для движения указателя, какой в какой момент двигать
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- не учел условие возврата индексов + 1
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## code
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### typescript
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```ts
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function twoSum(numbers: number[], target: number): number[] {
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let L = 0;
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let R = numbers.length - 1;
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while (L <= R) {
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const curSum = numbers[L] + numbers[R];
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if (curSum === target) return [L + 1, R + 1];
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curSum > target ? R-- : L++;
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}
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return [-1, -1];
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};
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```
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