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algorithmbasic2020/src/class11/Code02_PrintAllSubsquences....

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package class11;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
public class Code02_PrintAllSubsquences {
public static List<String> subs(String s) {
char[] str = s.toCharArray();
String path = "";
List<String> ans = new ArrayList<>();
process1(str, 0, ans, path);
return ans;
}
public static void process1(char[] str, int index, List<String> ans, String path) {
if (index == str.length) {
ans.add(path);
return;
}
String no = path;
process1(str, index + 1, ans, no);
String yes = path + String.valueOf(str[index]);
process1(str, index + 1, ans, yes);
}
public static List<String> subsNoRepeat(String s) {
char[] str = s.toCharArray();
String path = "";
HashSet<String> set = new HashSet<>();
process2(str, 0, set, path);
List<String> ans = new ArrayList<>();
for (String cur : set) {
ans.add(cur);
}
return ans;
}
public static void process2(char[] str, int index, HashSet<String> set, String path) {
if (index == str.length) {
set.add(path);
return;
}
String no = path;
process2(str, index + 1, set, no);
String yes = path + String.valueOf(str[index]);
process2(str, index + 1, set, yes);
}
public static void main(String[] args) {
String test = "aacc";
List<String> ans1 = subs(test);
List<String> ans2 = subsNoRepeat(test);
for (String str : ans1) {
System.out.println(str);
}
System.out.println("=================");
for (String str : ans2) {
System.out.println(str);
}
System.out.println("=================");
}
}