Solution.go

type pair struct {
	c byte
	x int
}

type StringIterator struct {
	d []pair
	p int
}

func Constructor(compressedString string) StringIterator {
	n := len(compressedString)
	i := 0
	d := []pair{}
	for i < n {
		c := compressedString[i]
		x := 0
		i++
		for i < n && compressedString[i] >= '0' && compressedString[i] <= '9' {
			x = x*10 + int(compressedString[i]-'0')
			i++
		}
		d = append(d, pair{c, x})
	}
	return StringIterator{d, 0}
}

func (this *StringIterator) Next() byte {
	if !this.HasNext() {
		return ' '
	}
	ans := this.d[this.p].c
	this.d[this.p].x--
	if this.d[this.p].x == 0 {
		this.p++
	}
	return ans
}

func (this *StringIterator) HasNext() bool {
	return this.p < len(this.d) && this.d[this.p].x > 0
}

/**
 * Your StringIterator object will be instantiated and called as such:
 * obj := Constructor(compressedString);
 * param_1 := obj.Next();
 * param_2 := obj.HasNext();
 */