Amazon.cpp

#include <iostream>
#include <stdlib.h>
#include <string.h>
 
using namespace std;

inline int compare (const void *a, const void * b) {  return ( *(char *)a - *(char *)b ); }
 
void swap (char* a, char* b) {
    char t = *a;
    *a = *b;
    *b = t;
}
int findCeil (char str[], char first, int l, int h) {
    int ceilIndex = l;
    for (int i = l+1; i <= h; i++)
      if (str[i] > first && str[i] < str[ceilIndex])
            ceilIndex = i;
 
    return ceilIndex;
}

char * ans ( char str[], int n)
{
    int size = strlen(str);
    qsort( str, size, sizeof( str[0] ), compare );
 	int count=0;
    bool isFinished = false;
    
    while ( ! isFinished )
    {
		if(++count == n)
			return str;
        int i;
        for ( i = size - 2; i >= 0; --i )
           if (str[i] < str[i+1])
              break;
              
        if ( i == -1 )
            isFinished = true;
        else
        {
            int ceilIndex = findCeil( str, str[i], i + 1, size - 1 );
            swap( &str[i], &str[ceilIndex] );
            qsort( str + i + 1, size - i - 1, sizeof(str[0]), compare );
        }
    }
}
int main()
{
	int test;
	
    char str[] = "ABCD";
    int n=3;
    cout<<sortedPermutations( str, n );
    return 0;
}