package Week_04.id_18;

import java.util.ArrayList;

import java.util.List;

/**

* @author LiveForExperience

* @date 2019/6/27 12:47

*/

public class LeetCode_784_18 {

List<String> list = new ArrayList<>();

public List<String> letterCasePermutation(String S) {

dfs(new StringBuilder(S), 0);

return list;

}

private void dfs(StringBuilder sb, int index) {

if (index == sb.length()) {

list.add(sb.toString());

return;

}

if (Character.isDigit(sb.charAt(index))) {

dfs(sb, index + 1);

} else {

char c = sb.charAt(index);

sb.setCharAt(index, Character.toLowerCase(c));

dfs(sb, index + 1);

sb.setCharAt(index, Character.toUpperCase(c));

dfs(sb, index + 1);

}

}

public List<String> letterCasePermutation1(String S) {

dfs(S.toCharArray(), 0);

return list;

}

private void dfs(char[] cs, int index) {

if (index == cs.length) {

list.add(new String(cs));

return;

}

if (cs[index] < 'A') {

dfs(cs, index + 1);

} else {

char c = cs[index];

if (c > 64 && c < 91) {

dfs(cs, index + 1);

cs[index] = (char) (cs[index] + 'a' - 'A');

dfs(cs, index + 1);

} else {

dfs(cs, index + 1);

cs[index] = (char) (cs[index] + 'A' - 'a');

dfs(cs, index + 1);

}

}

}

}