n個數的全排列C語言遞迴 （回溯）back-tracking

#include <stdio.h>#include <string.h>int n, a[100];int used[100];int num[100];void dfs( int x ){int i;if( x >= n ){for( i = 0; i < n; i++ )printf( "%d ", num[i] );printf( "\n" );}else{for( i = 0; i < n; i++ )if( !used[i] ){num[x] = a[i];used[i] = 1;dfs( x+1 );used[i] = 0;}}return ;}int main(){int i;memset( used, 0, sizeof(used) );printf( "此程式為遞迴進行n個整數的全排列(n<100),");printf( "一共有多少個數?\n");scanf( "%d", &n );for( i = 0; i < n; i++ ){printf( "第%d個:" );scanf( "%d", &a[i] );}dfs( 0 );return 0;}