# Valid Parenthesis Problem Index Out of Range (Go)

## Issue

I was converting code for a problem I previously solved in Python into Go and ran into a runtime error: index out of range  with length 1 on this line

`````` if string(s[i]) == ")" && arr[len(s) - 1] == "("{
``````

Here is the code in entirety.

``````func isValid(s string) bool {
arr := make([]string, 0)
if len(s) < 2 {
return false
}

for i := 0; i < len(s); i++ {

if string(s[i]) == "(" || string(s[i]) == "[" || string(s[i]) == "{" {
arr = append(arr, string(s[i]))
} else if string(s[i]) == ")" || string(s[i]) == "]" || string(s[i]) == "}" {
if len(arr) >= 1 {
if string(s[i]) == ")" && arr[len(s) - 1] == "("{
arr = arr[:len(arr) -1]
} else if string(s[i]) == "]" && arr[len(s) - 1] == "[" {
arr = arr[:len(arr) -1]
} else if string(s[i]) == "}" && arr[len(s) - 1] == "{" {
arr = arr[:len(arr) -1]
}  else {
return false
}
}else {
return false
}
}
}
if reflect.DeepEqual(arr, []string{""}) {
return true
} else  {
return false
}

}

``````

What is the cause of the issue?

## Solution

You’ve used `len(s)-1` to find the last index of `arr`, but it should be `len(arr)-1`.

Here’s a working version of your code, that fixes some additional bugs, and avoids needless conversion to string for single characters. https://go.dev/play/p/sazf2RguoIr

``````package main

import "fmt"

func isValid(s string) bool {
var arr []rune
for _, c := range s {
if c == '(' || c == '[' || c == '{' {
arr = append(arr, c)
} else if c == ')' || c == ']' || c == '}' {
if len(arr) == 0 {
return false
}
var last rune
arr, last = arr[:len(arr)-1], arr[len(arr)-1]
if c == ')' && last != '(' || c == ']' && last != '[' || c == '}' && last != '{' {
return false
}
}
}
return len(arr) == 0
}

func main() {
cases := []string{
"()[({}())]",
"(]",
"((())",
"{{{}}}",
"{{{[][][]}}}",
}
for _, c := range cases {
fmt.Println(c, isValid(c))
}
}
``````

Answered By – Paul Hankin

Answer Checked By – Senaida (GoLangFix Volunteer)