Slightly shorter solution.

1 files changed, 8 insertions, 24 deletions

diff --git a/permute.cpp b/permute.cpp
index 741455f..0829550 100644
--- a/permute.cpp
+++ b/permute.cpp
@@ -5,17 +5,10 @@
 #include <string>
 #include <vector>
 #include <algorithm>
+#include <iterator>
 
 using namespace std;
 
-struct string_printer : unary_function<void, string>
-{
-    void operator()(const string& s)
-    {
-        cout << s << endl;
-    }
-};
-
 void do_permute(const string& pool, string& perm, vector<string>& perms)
 {
     if (pool.empty())
@@ -28,6 +21,7 @@ void do_permute(const string& pool, string& perm, vector<string>& perms)
     for (size_t i = 0; i < n; ++i)
     {
         string tmp;
+        tmp.reserve(n-1);
         for (size_t j = 0; j < n; ++j)
         {
             if (i == j)
@@ -40,25 +34,15 @@ void do_permute(const string& pool, string& perm, vector<string>& perms)
     }
 }
 
-void permute(const char* s, size_t n)
+void permute(const string& pool)
 {
     vector<string> perms;
-    for (size_t i = 0; i < n; ++i)
-    {
-        string remain, perm;
-        for (size_t j = 0; j < n; ++j)
-        {
-            if (i == j)
-                perm.push_back(s[j]);
-            else
-                remain.push_back(s[j]);
-        }
-        do_permute(remain, perm, perms);
-        perm.resize(perm.size()-1);
-    }
+    string perm;
+    perm.reserve(pool.size());
+    do_permute(pool, perm, perms);
 
     cout << "number of permutations: " << perms.size() << endl;
-    for_each(perms.begin(), perms.end(), string_printer());
+    copy(perms.begin(), perms.end(), ostream_iterator<string>(cout, "\n"));
 }
 
 int main(int argc, char** argv)
@@ -68,7 +52,7 @@ int main(int argc, char** argv)
 
     size_t n = strlen(argv[1]);
     cout << "input string: " << argv[1] << " (len = " << n << ")" << endl;
-    permute(argv[1], n);
+    permute(string(argv[1],n));
 
     return EXIT_SUCCESS;
 }