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Solution.java
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119 lines (107 loc) · 3.93 KB
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package algorithm;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
/**
* 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。
* <p>
* 有效的 IP 地址正好由四个整数（每个整数位于 0 到 255 之间组成），整数之间用 '.' 分隔。
* <p>
* leetCode 93
* <p>
* 输入: "25525511135"
* 输出: ["255.255.11.135", "255.255.111.35"]
*
* @author Hikari
* @version 1.0.0
* @ClassName Solution.java
* @createTime 2020年08月09日 10:12:00
*/
public class Solution {
private final static List<String> res = new ArrayList<>();
private final static int DEF = 4;
private final static int MIN_SIZE = 3;
public static void main(String[] args) {
new Solution().restoreIpAddresses("25525511135");
}
public List<String> restoreIpAddresses(String s) {
List<String> ret = new ArrayList<>();
StringBuilder ip = new StringBuilder();
for (int a = 1; a < 4; ++a) {
for (int b = 1; b < 4; ++b) {
for (int c = 1; c < 4; ++c) {
for (int d = 1; d < 4; ++d) {
if (a + b + c + d == s.length()) {
int n1 = Integer.parseInt(s.substring(0, a));
int n2 = Integer.parseInt(s.substring(a, a + b));
int n3 = Integer.parseInt(s.substring(a + b, a + b + c));
int n4 = Integer.parseInt(s.substring(a + b + c));
if (n1 <= 255 && n2 <= 255 && n3 <= 255 && n4 <= 255) {
ip.append(n1).
append('.').
append(n2).
append('.').
append(n3).
append('.').append(n4);
if (ip.length() == s.length() + 3) {
ret.add(ip.toString());
}
ip.delete(0, ip.length());
}
}
}
}
}
}
return ret;
}
/* public List<String> restoreIpAddresses(String s) {
if (s.length() < DEF || Objects.isNull(s)) {
return res;
}
for (int i = 1; i < s.length() && i <= MIN_SIZE; ++i) {
for (int j = i; j < s.length() && j <= i + MIN_SIZE; ++j) {
for (int k = j; k < s.length() && k <= j + MIN_SIZE; ++k) {
String s1 = s.substring(0, i);
String s2 = s.substring(i, j);
String s3 = s.substring(j, k);
String s4 = s.substring(k);
if (trueOrFalse(s1) &&
trueOrFalse(s2) &&
trueOrFalse(s3) &&
trueOrFalse(s4)) {
StringBuilder sb = new StringBuilder();
sb.append(s1);
sb.append(".");
sb.append(s2);
sb.append(".");
sb.append(s3);
sb.append(".");
sb.append(s4);
res.add(sb.toString());
}
}
}
}
return res;
}
*/
public static boolean trueOrFalse(String string) {
if (string.length() == 0) {
return false;
}
if (string.length() == 1) {
return true;
}
if (string.length() > MIN_SIZE) {
return false;
}
if (string.charAt(0) == '0') {
return true;
}
if (Integer.parseInt(string) <= 255) {
return true;
}
return false;
}
}