leetcode: Two Sum II - Input Array Is Sorted

Problem

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

Two Pointers

class Solution {
    
    /**
     * \param numbers increasing order
     */
    fun twoSum(numbers: IntArray, target: Int): IntArray {
        val result = IntArray(2) { 0 }
        val size = numbers.size
        var s = 0
        var e = size - 1
        
        while (s < e) {
            if (numbers[s] + numbers[e] < target) s++
            else if (numbers[s] + numbers[e] > target) e--
            else {
                result[0] = s + 1
                result[1] = e + 1
                break
            }
        }
        return result
    }
}

Binary Search

class Solution {
    
    /**
     * \param numbers increasing order
     */
    fun twoSum(numbers: IntArray, target: Int): IntArray {
        val result = IntArray(2) { 0 }
        val size = numbers.size
        
        for (i in numbers.indices) {
            val key = target - numbers[i]
            var s = i + 1
            var e = size - 1
            while (s <= e) {
                val mid = s + (e - s) / 2
                if (numbers[mid] > key) e = mid - 1
                else if (numbers[mid] < key) s = mid + 1
                else {
                    result[0] = i + 1
                    result[1] = mid + 1
                    return result
                }
            }
        }       
        return result
    }
}