请问大神这里为什么要减1呢？感觉这里写的太繁琐了

[Lcoderfit]

samples/shorturl/models/model.go

Line 40 in 1c696ee

runes = append(runes, alpha[num-1])

[Lcoderfit]

for num > 0 {
	runes = append(runes, alpha[num%62])
	num = num / 62
}