全排列（dfs）

#include <stdio.h>#include <stdlib.h>char data[6] = {'A','B','C','D','E','F'};char data1[6];int count=0;bool isSafe(int x,int y){bool ret = true;for(int i=0;i<x;i++){if(data[y]==data1[i])ret = false;}return ret;}void print(){for(int i=0;i<6;i++){printf("%c",data1[i]);}printf("\n");}void func(int step){if(step == 6){print();count++;return;}for(int i=0;i<6;i++){if(isSafe(step,i)){data1[step]=data[i];func(step+1);}}}void main(){func(0);printf("%d\n",count);}