Add 784_Letter_Case_Permutation.java

Author: Sean Prashad

Subsets/.gitkeep

@@ -0,0 +1,29 @@
+class Solution {
+ public List<String> letterCasePermutation(String S) {
+ if (S == null || S.length() == 0) {
+ return Collections.emptyList();
+ }
+
+ List<String> result = new ArrayList<>();
+ dfs(S.toCharArray(), 0, result);
+ return result;
+ }
+
+ private void dfs(char[] word, int idx, List<String> result) {
+ if (idx == word.length) {
+ result.add(new String(word));
+ return;
+ }
+
+ if (Character.isDigit(word[idx])) {
+ dfs(word, idx + 1, result);
+ return;
+ }
+
+ word[idx] = Character.toLowerCase(word[idx]);
+ dfs(word, idx + 1, result);
+
+ word[idx] = Character.toUpperCase(word[idx]);
+ dfs(word, idx + 1, result);
+ }
+}