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Implementing Permutation Variations

, 14 Jul 2004 CPOL
Several enhanced permutation algorithms created in iterative or recursive solution.
// ============================================================================
// File:   EnhPerRe.cpp - Testing RecPermutation
// Author: Zuoliu Ding, May 2004
// ============================================================================
#include <string>
#include <vector>
using namespace std;

// ============================================================================
// Function:    RecPermutation - Enhanced Permutation Recursion
// Description: Generate all Permuted strings for an input string
// Parameter:   sz:   [in] an input string.
//              bRepeated: [in] Allow element repeated or not
// Return:      A vector of all Permuted strings.
// ============================================================================
vector<string> RecPermutation(const char* sz, 
                              bool bRepeated)
   vector<string> v, v1;
   string s1;    char ch;
   int nLen = strlen(sz);      

   if (nLen==1)            // Base case: Add one-char string
      v.insert(v.end(), sz);      
   else                    // nLen > 1, need recursion
      for (int i=0; i<nLen; i++)
         ch = sz[i];       // Extract each char as the first

         // To exclude repeated element
         if (!bRepeated)
            for (int j=0; j<i; j++)
               if (ch==sz[j]) break;

            if (j<i) continue;   // If i==j, Not a repeated one

         s1 = sz;           // Copy the original string
         s1.erase(i, 1);    // Put the rest string into s1

         v1 = RecPermutation(s1.c_str(), 
                        bRepeated); // Recursive 

         for (int i=0; i < (int)v1.size(); i++)
            s1 = ch + v1[i];   
            v.insert(v.end(), s1);   

   return v;

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About the Author

Zuoliu Ding
Software Developer
United States United States
An Adjunct Faculty and Software Developer in Los Angeles and Orange County, CA

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