akamig.ts

const arr = [8, 9, 1, 2, 3]
const limit = 6

const akamigSum = (arr: readonly number[], x: number) =>
	arr
		.map(item => item + x)
		.filter(item => item > 0)
		.reduce((a, b) => a + b)

const fib = (arr: readonly number[], limit: number) => {
	let xMin = -Math.max(...arr)
	let xMax = 0

	while (xMin < xMax) {
		const xMid = Math.floor((xMin + xMax) / 2)
		const sum = akamigSum(arr, xMid)

		if (sum === limit) return xMid
		if (sum < limit) {
			xMin = xMid + 1
			continue
		}
		if (sum > limit) {
			xMax = xMid - 1
			continue
		}
	}

	// 근처에 있는 x (xMin, xMax) 중 작은 거
	return xMin
}

console.log(fib(arr, limit))