ソリューションオプション：
#include <stdio.h> #include <string.h> #include <math.h> // A utility function to swap characters void swap ( char* a, char* b ) { char t = *a; *a = *b; *b = t; } // A utility function to reverse string str[low..high] void reverse ( char* str, int low, int high ) { while ( low < high ) { swap( &str[low], &str[high] ); ++low; --high; } } // Cycle leader algorithm to move all even positioned elements // at the end. void cycleLeader ( char* str, int shift, int len ) { int j; char item; for (int i = 1; i < len; i *= 3 ) { j = i; item = str[j + shift]; do { // odd index if ( j & 1 ) j = len / 2 + j / 2; // even index else j /= 2; // keep the back-up of element at new position swap (&str[j + shift], &item); } while ( j != i ); } } // The main function to transform a string. This function mainly uses // cycleLeader() to transform void moveNumberToSecondHalf( char* str ) { int k, lenFirst; int lenRemaining = strlen( str ); int shift = 0; while ( lenRemaining ) { k = 0; // Step 1: Find the largest prefix subarray of the form 3^k + 1 while ( pow( 3, k ) + 1 <= lenRemaining ) k++; lenFirst = pow( 3, k - 1 ) + 1; lenRemaining -= lenFirst; // Step 2: Apply cycle leader algorithm for the largest subarrau cycleLeader ( str, shift, lenFirst ); // Step 4.1: Reverse the second half of first subarray reverse ( str, shift / 2, shift - 1 ); // Step 4.2: Reverse the first half of second sub-string. reverse ( str, shift, shift + lenFirst / 2 - 1 ); // Step 4.3 Reverse the second half of first sub-string and first // half of second sub-string together reverse ( str, shift / 2, shift + lenFirst / 2 - 1 ); // Increase the length of first subarray shift += lenFirst; } } // Driver program to test above function int main() { char str[] = "a1b2c3d4e5f6g7"; moveNumberToSecondHalf( str ); printf( "%s", str ); return 0; }