Uva 10098 Generating Fast

题目：http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=107&page=show_problem&problem=1039
具体思路请参考刘汝佳的《算法竞赛入门经典》7.2.2生成可重集的排列

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 11

char A[MAX],P[MAX];

void print_permutation(int len,int cur)
{
	int i,j;
	if(cur==len)
	{
		A[cur]='\0';
		puts(A);
	}
	else
	{
		for(i=0;i<len;i++)
			if(i==0||P[i]!=P[i-1])
			{
				int c1=0,c2=0;
				for(j=0;j<cur;j++)
					if(A[j]==P[i])
						c1++;
				for(j=0;j<len;j++)
					if(P[j]==P[i])
						c2++;
				if(c1<c2)
				{
					A[cur]=P[i];
					print_permutation(len,cur+1);
				}
			}
	}
}
int cmp(void const *a,void const *b)
{
	return *((char *)a)-*((char *)b);
}
int main()
{
	int N,len;
	scanf("%d",&N);
	while(N--)
	{
		scanf("%s",P);
		len=strlen(P);
		qsort(P,len,1,cmp);
		print_permutation(len,0);
		putchar('\n');
	}
	return 0;
}