0784 solved.

0784-Letter-Case-Permutation/cpp-0784/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.5)
+project(cpp_0784)
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+
+set(SOURCE_FILES main2.cpp)
+add_executable(cpp_0784 ${SOURCE_FILES})

0784-Letter-Case-Permutation/cpp-0784/main.cpp

@@ -0,0 +1,71 @@
+/// Source : https://leetcode.com/problems/letter-case-permutation/description/
+/// Author : liuyubobobo
+/// Time   : 2018-03-09
+
+#include <iostream>
+#include <vector>
+#include <cassert>
+#include <ctype.h>
+
+using namespace std;
+
+/// Backtrack
+///
+/// Time Complexity: O(2^len(S))
+/// Space Complexity: O(len(S))
+class Solution {
+
+public:
+    vector<string> letterCasePermutation(string S) {
+
+        for(int i = 0 ; i < S.size() ; i ++)
+            if(isupper(S[i]))
+                S[i] = tolower(S[i]);
+
+        vector<string> res;
+        solve(S, 0, res);
+        return res;
+    }
+
+private:
+    void solve(string& S, int index, vector<string>& res){
+
+        if(index == S.size()){
+            res.push_back(S);
+            return;
+        }
+
+        if(isalpha(S[index])){
+            assert(islower(S[index]));
+            solve(S, index + 1, res);
+            S[index] = toupper(S[index]);
+            solve(S, index + 1, res);
+            S[index] = tolower(S[index]);
+        }
+        else{
+            assert(isdigit(S[index]));
+            solve(S, index + 1, res);
+        }
+    }
+};
+
+
+void print_vec(const vector<string>& vec){
+    for(string s: vec)
+        cout << s << " ";
+    cout << endl;
+}
+
+int main() {
+
+    print_vec(Solution().letterCasePermutation("a1b2"));
+    cout << endl;
+
+    print_vec(Solution().letterCasePermutation("3z4"));
+    cout << endl;
+
+    print_vec(Solution().letterCasePermutation("12345"));
+    cout << endl;
+
+    return 0;
+}

0784-Letter-Case-Permutation/cpp-0784/main2.cpp

@@ -0,0 +1,65 @@
+/// Source : https://leetcode.com/problems/letter-case-permutation/description/
+/// Author : liuyubobobo
+/// Time   : 2018-03-09
+
+#include <iostream>
+#include <vector>
+#include <cassert>
+#include <ctype.h>
+
+using namespace std;
+
+/// Binary Code
+///
+/// Time Complexity: O(2^len(S))
+/// Space Complexity: O(len(S))
+class Solution {
+
+public:
+    vector<string> letterCasePermutation(string S) {
+
+        int n = 0;
+        for(int i = 0 ; i < S.size() ; i ++)
+            if(isalpha(S[i])){
+                S[i] = tolower(S[i]);
+                n ++;
+            }
+
+        vector<string> res;
+        for(int i = 0 ; i < (1<<n) ; i ++){
+
+            int k = 0;
+            for(int j = 0 ; j < S.size() ; j ++)
+                if(isalpha(S[j])){
+                    if(i & (1<<k))
+                        S[j] = toupper(S[j]);
+                    else
+                        S[j] = tolower(S[j]);
+                    k ++;
+                }
+            res.push_back(S);
+        }
+        return res;
+    }
+};
+
+
+void print_vec(const vector<string>& vec){
+    for(string s: vec)
+        cout << s << " ";
+    cout << endl;
+}
+
+int main() {
+
+    print_vec(Solution().letterCasePermutation("a1b2"));
+    cout << endl;
+
+    print_vec(Solution().letterCasePermutation("3z4"));
+    cout << endl;
+
+    print_vec(Solution().letterCasePermutation("12345"));
+    cout << endl;
+
+    return 0;
+}

readme.md

@@ -258,6 +258,7 @@ email: [[email protected]](mailto:[email protected])
 | 781 | [Rabbits in Forest](https://leetcode.com/problems/rabbits-in-forest/description/) | [solution](https://leetcode.com/problems/rabbits-in-forest/solution/) | [C++](0781-Rabbits-in-Forest/cpp-0781/) | | |
 | | | | | | |
 | 783 | [Minimum Distance Between BST Nodes](https://leetcode.com/problems/minimum-distance-between-bst-nodes/description/) | [solution](https://leetcode.com/problems/minimum-distance-between-bst-nodes/solution/) | [C++](0783-Minimum-Distance-Between-BST-Nodes/cpp-0783/) | | |
+| 784 | [Letter Case Permutation](https://leetcode.com/problems/letter-case-permutation/description/) | [solution](https://leetcode.com/problems/letter-case-permutation/solution/) | [C++](0784-Letter-Case-Permutation/cpp-0784/) | | |
 | | | | | | |
 | 788 | [Rotated Digits](https://leetcode.com/problems/rotated-digits/description/) | [solution](https://leetcode.com/problems/rotated-digits/solution/) | [C++](0788-Rotated-Digits/cpp-0788/) | | |
 | 789 | [Escape The Ghosts](https://leetcode.com/problems/escape-the-ghosts/description/) | [solution](https://leetcode.com/problems/escape-the-ghosts/solution/) | [C++](0789-Escape-The-Ghosts/cpp-0789/) | | |