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include/s0093_restore_ip_addresses.hpp
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14
include/s0093_restore_ip_addresses.hpp
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@ -0,0 +1,14 @@
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#ifndef S0093_RESTORE_IP_ADDRESSES_HPP
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#define S0093_RESTORE_IP_ADDRESSES_HPP
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#include <string>
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#include <vector>
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using namespace std;
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class S0093 {
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public:
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vector<string> restoreIpAddresses(string s);
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};
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#endif
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@ -28,10 +28,15 @@ void backtrack(NodeState &node, vector<NodeState> &result, int para1, int para2,
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return;
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}
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// 剪枝
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// 当现在的节点不可能出现我们想要的结果时,直接跳过。
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if (/* out of scope */) {
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return;
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}
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// 遍历该节点的所有子节点,即遍历下一层
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for (...) {
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// 剪枝
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// 当现在的节点不可能出现我们想要的结果时,直接跳过。
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// 剪枝也可以在 for 循环中完成
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if (/* out of scope */) {
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continue;
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}
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@ -3,3 +3,5 @@
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## [131. 分割回文串](https://leetcode.cn/problems/palindrome-partitioning/)
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![](https://paste.sainnhe.dev/FHTE.jpg)
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## [93. 复原 IP 地址](https://leetcode.cn/problems/restore-ip-addresses/)
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55
src/s0093_restore_ip_addresses.cpp
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src/s0093_restore_ip_addresses.cpp
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#include "s0093_restore_ip_addresses.hpp"
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bool isValidIpAddressSegment(const string &s, int begin, int end) {
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if (begin > end) {
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return false;
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}
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if (s[begin] == '0' && begin != end) { // 0开头的数字不合法
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return false;
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}
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int num = 0;
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for (int i = begin; i <= end; i++) {
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if (s[i] > '9' || s[i] < '0') { // 遇到非数字字符不合法
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return false;
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}
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num = num * 10 + (s[i] - '0');
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if (num > 255) { // 如果大于255了不合法
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return false;
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}
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}
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return true;
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}
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void restoreIpAddressesDFS(vector<int> &dots, vector<string> &result, string &s,
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int startIndex) {
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// 结束条件
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if (dots.size() == 4 && startIndex == s.length()) {
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string ip = s.substr(0, dots[0] + 1) + "." +
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s.substr(dots[0] + 1, dots[1] - dots[0]) + "." +
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s.substr(dots[1] + 1, dots[2] - dots[1]) + "." +
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s.substr(dots[2] + 1, dots[3] - dots[2]);
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result.push_back(ip);
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}
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// 剪枝
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// 如果已经分成了四段,就没必要再分了
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if (dots.size() == 4) {
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return;
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}
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// 遍历当前节点的下一层
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for (int i = startIndex; i < startIndex + 3; ++i) {
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if (isValidIpAddressSegment(s, startIndex, i)) {
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dots.push_back(i);
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restoreIpAddressesDFS(dots, result, s, i + 1);
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dots.pop_back();
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}
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}
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}
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vector<string> S0093::restoreIpAddresses(string s) {
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vector<string> result{};
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vector<int> dots{};
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restoreIpAddressesDFS(dots, result, s, 0);
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return result;
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}
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