英文:
len() is not giving me the right result
问题
s1和s2在连接字符串后应该具有相同的长度，长度应该是相等的。
package main
import . "fmt"
func stamp(s1 string, s2 string) (result string){
if len(s1) > len(s2) {
for i := 0; i < (len(s1) - len(s2)); i++{
s2 += "-"
}
} else if len(s1) < len(s2) {
for i := 0; i < (len(s2) - len(s1)); i++ {
s1 += "-"
}
}
for i := 0; i < len(s2); i++ {
result += string(s1[i]) + string(s2[i])
}
return
}
func main(){
var s1, s2 string
Print("插入两个单词：")
Scan(&s1, &s2)
Println(stamp(s1,s2))
}
尝试将s1设置为"esame"，s2设置为"go"，stamp得到的结果是egsoa-m-，应该是egsoa-m-e-。
尝试将s2设置为"go"，s1设置为"esame"，stamp得到的结果是：
panic: runtime error: index out of range [4] with length 4
goroutine 1 [running]:
main.stamp(...)
/home/Usr/Info/es19.go:16
main.main()
/home/Usr/Info/es19.go:25 +0x2ac
exit status 2
英文:
The lenght of s1 and s2 should be the same after concatenating "-" to the string to have the same lenght
package main
import . "fmt"
func stamp(s1 string, s2 string) (result string){
if len(s1) > len(s2) {
for i := 0; i < (len(s1) - len(s2)); i++{
s2 += "-"
}
} else if len(s1) < len(s2) {
for i := 0; i < (len(s2) - len(s1)); i++ {
s1 += "-"
}
}
for i := 0; i < len(s2); i++ {
result += string(s1[i]) + string(s2[i])
}
return
}
func main(){
var s1, s2 string
Print("Insert 2 words: ")
Scan(&s1, &s2)
Println(stamp(s1,s2))
}
Tried s1 as "esame"
s2 as "go"
stamp got egsoa-m- // should be egsoa-m-e-
Tried s2 as "go"
s1 as "esame"
stamp got
panic: runtime error: index out of range [4] with length 4
goroutine 1 [running]:
main.stamp(...)
/home/Usr/Info/es19.go:16
main.main()
/home/Usr/Info/es19.go:25 +0x2ac
exit status 2
答案1
得分: 1
这是一个常见的编程陷阱，即在访问数组/切片时不应该修改它。在这种情况下，你试图在遍历过程中向s1/s2追加“-”，而for循环依赖于len(s1)和len(s2)的差值。假设s1和s2的初始长度分别为2和5，差值为3，在第一轮之后，s1的长度变为3，i变为1，差值变为2，循环继续。但是，在第二轮之后，s1的长度变为4，i变为2，差值现在为1，所以循环在这里结束。你可能期望有3轮循环，但实际上只有2轮。
更重要的是，Go语言的len函数是动态调用的。因此，解决方案是在for循环之前添加一行代码来保存初始长度差值，即下面的sub行。我相信这会得到你想要的结果。
if len(s1) > len(s2) {
sub := len(s1) - len(s2)
for i := 0; i < sub; i++ {
s2 += "-"
}
} else if len(s1) < len(s2) {
sub := len(s2) - len(s1)
for i := 0; i < sub; i++ {
s1 += "-"
}
}
英文:
This is a common programing pitfall which is that you shouldn't modify an/a array/slice while visiting it. In this case, you try to append '-' to s1/s2 while the for-loop depends on the subtraction of len(s1) and len(s2). Let's assume the initial length of s1 and s2 to be 2 and 5, the delta is 3, after the first round, length of s1 becomes 3 and the i becomes 1, the delta is 2, the loop continues. But, after the second round, length of s1 becomes 4 and i becomes 2, the delta is now 1, so the loop ends here. You may expect 3 rounds while it turns out to be 2.
More to learn is that Go's len function is dynamic called. So the solution is to add one line above the for-loop to save the initial length delta, which is the sub line below. I believe it will give what you want.
if len(s1) > len(s2) {
sub := len(s1) - len(s2)
for i := 0; i < sub; i++ {
s2 += "-"
}
} else if len(s1) < len(s2) {
sub := len(s2) - len(s1)
for i := 0; i < sub; i++ {
s1 += "-"
}
}
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