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  1. #include <iostream>
  2. #include <string>
  3. #include <algorithm>
  4. using namespace std;
  5.  
  6. char x[100];  // Stores the current permutation
  7. int n;
  8. char c;
  9. string input;  // Contains sorted letters from 'A' to c
  10. bool chuaxet[100];  // Tracks which characters are used
  11.  
  12. void Init() {
  13.     cin >> c;
  14.     input.resize(c - 'A' + 1);
  15.     for (int i = 0; i <= c - 'A'; i++) {
  16.         input[i] = 'A' + i;
  17.     }
  18.     sort(input.begin(), input.end());
  19.     fill(chuaxet, chuaxet + input.size(), true);
  20. }
  21.  
  22. // Checks if the current permutation (x) is valid
  23. bool isValidPermutation(int len) {
  24.     for (int i = 0; i < len - 1; i++) {
  25.         if ((x[i] == 'A' && x[i + 1] == 'E') || 
  26.             (x[i] == 'E' && x[i + 1] == 'A')) {
  27.             return false;
  28.         }
  29.     }
  30.     return true;
  31. }
  32.  
  33. void backtrack(int i) {
  34.     if (i == input.size()) {
  35.         // Print the permutation if valid
  36.         if (isValidPermutation(i)) {
  37.             for (int k = 0; k < i; k++) cout << x[k];
  38.             cout << endl;
  39.         }
  40.         return;
  41.     }
  42.  
  43.     for (int j = 0; j < input.size(); j++) {
  44.         if (chuaxet[j]) {
  45.             x[i] = input[j];  // Choose input[j] for position i
  46.             chuaxet[j] = false;  // Mark as used
  47.             backtrack(i + 1);  // Recurse
  48.             chuaxet[j] = true;  // Backtrack (unmark)
  49.         }
  50.     }
  51. }
  52.  
  53. int main() {
  54.     Init();
  55.     backtrack(0);
  56.     return 0;
  57. }
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin 
D
stdout 
ABCD
ABDC
ACBD
ACDB
ADBC
ADCB
BACD
BADC
BCAD
BCDA
BDAC
BDCA
CABD
CADB
CBAD
CBDA
CDAB
CDBA
DABC
DACB
DBAC
DBCA
DCAB
DCBA
https://ideone.com/XEk4t8
language:
C++ (gcc 8.3)
created:
238 days ago
visibility:
public

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