|
|
package class17;
|
|
|
|
|
|
import java.util.ArrayList;
|
|
|
import java.util.HashSet;
|
|
|
import java.util.List;
|
|
|
|
|
|
public class Code03_PrintAllSubsquences {
|
|
|
|
|
|
// s -> "abc" ->
|
|
|
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;
|
|
|
}
|
|
|
|
|
|
// str 固定参数
|
|
|
// 来到了str[index]字符，index是位置
|
|
|
// str[0..index-1]已经走过了！之前的决定，都在path上
|
|
|
// 之前的决定已经不能改变了，就是path
|
|
|
// str[index....]还能决定，之前已经确定，而后面还能自由选择的话，
|
|
|
// 把所有生成的子序列，放入到ans里去
|
|
|
public static void process1(char[] str, int index, List<String> ans, String path) {
|
|
|
if (index == str.length) {
|
|
|
ans.add(path);
|
|
|
return;
|
|
|
}
|
|
|
// 没有要index位置的字符
|
|
|
process1(str, index + 1, ans, path);
|
|
|
// 要了index位置的字符
|
|
|
process1(str, index + 1, ans, path + String.valueOf(str[index]));
|
|
|
}
|
|
|
|
|
|
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 = "acccc";
|
|
|
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("=================");
|
|
|
|
|
|
}
|
|
|
|
|
|
}
|
