示例:
输入: "25525511135"
输出: ["255.255.11.135", "255.255.111.35"]
const SEG_COUNT = 4
var (
ans []string
segments []int
)
func restoreIpAddresses(s string) []string {
segments = make([]int, SEG_COUNT)
ans = []string{}
dfs(s, 0, 0)
return ans
}
//segStart 对应字符串下标
//segId, 对应段数
func dfs(s string, segId, segStart int) {
if segId == SEG_COUNT {
if segStart == len(s) {
ipAddr := ""
for i := 0; i < SEG_COUNT; i++ {
ipAddr += strconv.Itoa(segments[i])
if i != SEG_COUNT - 1 {
ipAddr += "."
}
}
ans = append(ans, ipAddr)
}
return
}
if segStart == len(s) {
return
}
if s[segStart] == '0' {
segments[segId] = 0
dfs(s, segId + 1, segStart + 1)
}
// 一般情况，枚举每一种可能性并递归
addr := 0
for segEnd := segStart; segEnd < len(s); segEnd++ {
//取出当前的值
addr = addr * 10 + int(s[segEnd] - '0')
if addr > 0 && addr <= 0xFF {
//存储对应的IP值
segments[segId] = addr
dfs(s, segId + 1, segEnd + 1)
} else {
break
}
}
}
