替换Golang中第N个出现的字符串

Question

How do I replace the nth (in this case second) occurrence of a string in golang? The following code replaces the example string optimismo from optimism with o from optimism when I want it to be optimismo from

package main

import (
    "fmt"
    "strings"
)

func main() {
    mystring := "optimismo from optimism"
    excludingSecond := strings.Replace(mystring, "optimism", "", 1)
    fmt.Println(excludingSecond)
}

Answer 1

For example,

package main

import (
    "fmt"
    "strings"
)

// Replace the nth occurrence of old in s by new.
func replaceNth(s, old, new string, n int) string {
    i := 0
    for m := 1; m <= n; m++ {
        x := strings.Index(s[i:], old)
        if x < 0 {
            break
        }
        i += x
        if m == n {
            return s[:i] + new + s[i+len(old):]
        }
        i += len(old)
    }
    return s
}

func main() {
    s := "optimismo from optimism"
    fmt.Printf("%q
", s)
    t := replaceNth(s, "optimism", "", 2)
    fmt.Printf("%q
", t)
}

Output:

"optimismo from optimism"
"optimismo from "