leetcode-go/hard/564.find-the-closest-palindrome.go

func nearestPalindromic(n string) string {
	set := make([]int, 0, 5)
	l := len(n)
	set = append(set, int(math.Pow10(l))+1)
	set = append(set, int(math.Pow10(l-1))-1)
	r1, r2, r3 := []rune(n), []rune(n), []rune(n)
	beg, end := l/2-1+l&1, l/2
	if r1[beg] != '0' {
		r1[beg]--
	}
	if r3[beg] != '9' {
		r3[beg]++
	}
	for ; end < l; beg, end = beg-1, end+1 {
		r1[end] = r1[beg]
		r2[end] = r2[beg]
		r3[end] = r3[beg]
	}
	n1, _ := strconv.Atoi(string(r1))
	n2, _ := strconv.Atoi(string(r2))
	n3, _ := strconv.Atoi(string(r3))
	set = append(set, n1)
	set = append(set, n2)
	set = append(set, n3)
	num, _ := strconv.Atoi(n)
	min, res := math.MaxInt32, math.MaxInt32
	for _, i := range set {
		if det := abs(num - i); det != 0 && det < min || (det == min && i < res) {
			min, res = det, i
		}
	}
	return strconv.Itoa(res)
}

func minInt(x, y int) int {
	if x < y {
		return x
	}
	return y
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}