/*
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.
function minimal_two_sum(arr) {
// Handle edge case: need at least two elements
if (arr.length < 2) {
throw new Error("Array must contain at least two elements.");
}
// Initialize min1 and min2 to very large values
let min1 = Infinity;
let min2 = Infinity;
// Single pass through the array
for (const x of 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;
}
const arr = [7, -3, 10, 1, 5, 2, 4];
try {
const result = minimal_two_sum(arr);
console.log("Minimal sum of two elements:", result);
} catch (e) {
console.error("Error:", e.message);
}
/*
run:
Minimal sum of two elements: -2
*/
