hdu 1716 dfs写法

基础dfs，输出要求还真是多，可以用stl做，不过自己还是手写了一下。

#include <algorithm>
#include <iostream>
#include <cstring>
using namespace std;

const int N = 4;
const int M = 24;
const int K = 1000;
int index;
int num[N];
bool visit[N];
int tmp[N];
int ans[M + 1];
int cnt;

struct Node 
{
    int num[N];
} node[K];

void dfs( int i )
{
    if ( i == 4 )
    {
        int sum = 0;
        for ( int j = 0; j < 4; j++ )
        {
            sum = sum * 10 + tmp[j];
        }
        ans[cnt++] = sum;
        return ;
    }
    for ( int k = 0; k < 4; k++ )
    {
        if ( !visit[k] )
        {
            visit[k] = 1;
            tmp[i] = num[k];
            dfs( i + 1 );
            visit[k] = 0;            
        }
    }
}

void solve( int p )
{
    for ( int i = 0; i < N; i++ )
    {
        num[i] = node[p].num[i];
    }
    cnt = 0;
    memset( visit, 0, sizeof(visit) );    
    dfs(0);
    sort( ans, ans + cnt );
    for ( int i = 0; i < cnt - 1; i++ )
    {
        if ( ans[i] == ans[i + 1] )
        {
            for ( int j = i; j < cnt - 1; j++ )
            {
                ans[j] = ans[j + 1];
            }
            cnt--;
            i--;
        }
    }
    ans[cnt++] = 9999999;
    int i = 0;
    while ( ans[i] < 1000 ) i++;
    int sp = ans[i] / 1000;    
    for ( ; i < cnt - 1; i++ )
    {
        cout << ans[i];
        if ( ans[i + 1] / 1000 == sp ) 
        {
            cout << ' ';
        }
        else 
        {
            cout << endl;
            sp = ans[i + 1] / 1000;
        }
    }
}

int main()
{
    index = 0;
    while ( 1 )
    {
        int s = 0;
        for ( int i = 0; i < 4; i++ ) 
        {
            cin >> node[index].num[i];
            s += node[index].num[i];
        }
        if ( !s ) break;
        index++;
    }
    for ( int i = 0; i < index; i++ )
    {
        solve(i);
        if ( i != index - 1 ) cout << endl;
    }
    return 0;
}