package main
import (
"errors"
"fmt"
"math"
)
/*
Goal:
-----
Find the minimal value of (a[i] + a[j]) for any two distinct elements in an array.
Efficient Strategy (O(n)):
--------------------------
The smallest possible sum of two distinct elements is obtained by:
- finding the smallest element
- finding the second smallest element
Because any other pair must be >= one of these two.
We scan the array once, keeping track of:
- min1 = smallest element seen so far
- min2 = second smallest element seen so far
*/
// A function that computes the minimal sum of two distinct elements.
func minimalTwoSum(arr []int) (int, error) {
// Handle edge case: need at least two elements
if len(arr) < 2 {
return 0, errors.New("array must contain at least two elements")
}
// Initialize min1 and min2 to very large values
min1 := math.MaxInt
min2 := math.MaxInt
// Single pass through the array
for _, x := range arr {
if x < min1 {
// x becomes the new smallest; old min1 becomes min2
min2 = min1
min1 = x
} else if x < min2 {
// x is not the smallest, but smaller than the second smallest
min2 = x
}
}
// The minimal sum of two distinct elements
return min1 + min2, nil
}
func main() {
arr := []int{7, -3, 10, 1, 5, 2, 4}
result, err := minimalTwoSum(arr)
if err != nil {
fmt.Println("Error:", err)
return
}
fmt.Println("Minimal sum of two elements:", result)
}
/*
run:
Minimal sum of two elements: -2
*/
