LC: WC 450: Q1: Smallest Index with Digit Sum Equal to Index

func smallestIndex(nums []int) int {
    var numSum int
    for idx,num := range nums{
        numSum=0
        for num>0{
            numSum+=num%10
            num=num/10
        }
        if idx==numSum{
            return idx
        }
    }
    return -1
}