Compare two version strings
A deploy tool decides whether the version on the server is behind the one being released.
- Versions are dot-separated numbers: 1.2.10 has parts 1, 2 and 10.
- Compare part by part numerically, so 1.10 is above 1.2 — not below it, as a text sort would have it.
- A missing part counts as zero, so 1.2 and 1.2.0 are the same version.
- Leading zeros mean nothing: 1.01 is 1.1.
- Return -1 when the first is older, 1 when it is newer, 0 when they match.
compareVersions(first: string, second: string) → int
Go needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
func compareVersions(first string, second string) int {
}Worked examples
| Call | Result |
|---|---|
compareVersions("1.2.10", "1.10.2") | -1 |
compareVersions("1.2", "1.2.0") | 0 |
compareVersions("2.0", "1.9.9") | 1 |
compareVersions("1.0.0", "1.0.0") | 0 |
Hint
Walk both to the length of the longer one, reading a missing part as zero.
Reference solution in Go
func compareVersions(first string, second string) int {
a := strings.Split(first, ".")
b := strings.Split(second, ".")
n := len(a)
if len(b) > n {
n = len(b)
}
for i := 0; i < n; i++ {
x, y := 0, 0
if i < len(a) {
x, _ = strconv.Atoi(a[i])
}
if i < len(b) {
y, _ = strconv.Atoi(b[i])
}
if x != y {
if x < y {
return -1
}
return 1
}
}
return 0
}