Two Sum II - Input array is sorted

LeetCode 167번

Tags. array, binary Search, Two Pointers

 

https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/

Two Sum II - Input array is sorted - LeetCode

 

문제

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2.

Note:

• Your returned answers (both index1 and index2) are not zero-based.
• You may assume that each input would have exactly one solution and you may not use the same element twice.

Example:

Input: numbers = [2,7,11,15], target = 9

Output: [1,2]

Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

 

Solution

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int[] result = new int[2];
        int upperBound = numbers.length - 1;
        int lowerBound = 0;
        
        while(lowerBound <= upperBound) {
            
            
            if(target == numbers[lowerBound] + numbers[upperBound]) {
                result[0] = lowerBound + 1;
                result[1] = upperBound + 1;
                return result;
                
            }else if(numbers[lowerBound] + numbers[upperBound] > target) {
                upperBound--;
            }else {
                lowerBound ++;
            }
        }
        return result;
    }
}

 

Runtime : 1ms

Memory : 38.3MB