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78 lines
1.4 KiB
Markdown
Executable File
78 lines
1.4 KiB
Markdown
Executable File
# [93. Restore IP Addresses](https://leetcode.com/problems/restore-ip-addresses/)
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## 题目
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Given a string containing only digits, restore it by returning all possible valid IP address combinations.
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**Example**:
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Input: "25525511135"
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Output: ["255.255.11.135", "255.255.111.35"]
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## 题目大意
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给定一个只包含数字的字符串，复原它并返回所有可能的 IP 地址格式。
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## 解题思路
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- DFS 深搜
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- 需要注意的点是 IP 的规则，以 0 开头的数字和超过 255 的数字都为非法的。
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## 代码
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```go
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package leetcode
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import (
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"strconv"
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)
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func restoreIPAddresses(s string) []string {
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if s == "" {
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return []string{}
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}
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res, ip := []string{}, []int{}
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dfs(s, 0, ip, &res)
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return res
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}
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func dfs(s string, index int, ip []int, res *[]string) {
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if index == len(s) {
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if len(ip) == 4 {
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*res = append(*res, getString(ip))
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}
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return
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}
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if index == 0 {
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num, _ := strconv.Atoi(string(s[0]))
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ip = append(ip, num)
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dfs(s, index+1, ip, res)
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} else {
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num, _ := strconv.Atoi(string(s[index]))
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next := ip[len(ip)-1]*10 + num
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if next <= 255 && ip[len(ip)-1] != 0 {
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ip[len(ip)-1] = next
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dfs(s, index+1, ip, res)
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ip[len(ip)-1] /= 10
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}
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if len(ip) < 4 {
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ip = append(ip, num)
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dfs(s, index+1, ip, res)
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ip = ip[:len(ip)-1]
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}
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}
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}
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func getString(ip []int) string {
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res := strconv.Itoa(ip[0])
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for i := 1; i < len(ip); i++ {
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res += "." + strconv.Itoa(ip[i])
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}
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return res
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}
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``` |