twoSum函数在不同的数组输入下的行为不同

Question

When I run the following code, I get the expected answer [3, 4], which is the index of the 2 numbers that add up to my target variable. However, when I change the myArray input to []int{1,2,3,4,6,11,4,12} (I deleted the last 6), I get a panic. Please help me understand why this is happening.

func twoSum (nums []int, target int) []int {
    length := len(nums) - 1
    for i := range nums[:length] {
        for j := range nums[i + 1:] {
            if nums[i] + nums[j] == target {
                return []int{i, j}
                break
            }
        }
    }
    panic("should never happen")
}

func main() {
    myArray := []int{1,2,3,4,6,11,4,12}
    myTarget := 10
    fmt.Println(twoSum(myArray, myTarget))
}

Answer 1

for j := range nums[i + 1:] {

This does not work like you expect: j here is a 0-based index of a new slice, that you obtained after you resliced the nums with nums[i+1:].

If you still want to have the absolute index in the nums slice you need to offset it manually, eg:

jx := j + i + 1

and then use jx instead of j

Demo: https://play.golang.org/p/s7_tcHvu6fB

Alternatively you may have used a good old indexed for instead of for-range as a nested loop:

for j := i + 1; j < length; j++ {

Demo: https://play.golang.org/p/-yF7cWYgYri