带分数【dfs】

带分数

memcpy递归里面不能开太大阿

题意

简单dfs

• 枚举全1-9的全排列，for循环出a，b，c，判断结果，是的话res++

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<set>
#include<list>
#include<deque>
#include<map>
#include<queue>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define mst(s,_s) memset(s, _s, sizeof(s))
const double PI = acos(-1.0);
const double eps = 1e-6;
const int INF = 0x3f3f3f3f;
const int N = 1e6+100;
int T,n,m;
int st[N];
int res=0;
int cnt[N];

int get_num(int i,int j){
    int res=0;
    for(int k=i;k<=j;k++)
    {
        res=res*10+cnt[k];
    }
    return res;
}
void dfs(int u)
{
    if(u>9)
    {
        
        int a=0,b=0,c=0;
        for(int i=1;i<=7;i++)
        {
            for(int j=i+1;j<=8;j++){
                a=get_num(1,i);
                b=get_num(i+1,j);
                c=get_num(j+1,9);
                if((n-a)*c==b)
                {
                    res++;
                    //cout<<a<<' '<<b<<' '<<c<<endl;
                }
            }
           
        }
    }
    for(int i=1;i<=9;i++)
    {
        if(st[i]) continue;
        st[i]=1;
        cnt[u]=i;
        dfs(u+1);
        st[i]=0;
        cnt[u]=0;
    }
}


int main() {
    cin>>n;
    dfs(1);
    cout<<res<<endl;
    return 0;
}

dfs嵌套

• 先dfs出a，然后在a的基础上dfs出b，再判断

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 10;

int n;
bool st[N], backup[N];
int ans;

bool check(int a, int c)
{
    long long b = n * (long long)c - a * c;

    if (!a || !b || !c) return false;

    memcpy(backup, st, sizeof st);//递归memcpy，不能开太大
    while (b)
    {
        int x = b % 10;     // 取个位
        b /= 10;    // 个位删掉
        if (!x || backup[x]) return false;
        backup[x] = true;
    }

    for (int i = 1; i <= 9; i ++ )
        if (!backup[i])
            return false;

    return true;
}

void dfs_c(int u, int a, int c)
{
    if (u > 9) return;

    if (check(a, c)) ans ++ ;

    for (int i = 1; i <= 9; i ++ )
        if (!st[i])
        {
            st[i] = true;
            dfs_c(u + 1, a, c * 10 + i);
            st[i] = false;
        }
}

void dfs_a(int u, int a)
{
    if (a >= n) return;
    if (a) dfs_c(u, a, 0);

    for (int i = 1; i <= 9; i ++ )
        if (!st[i])
        {
            st[i] = true;
            dfs_a(u + 1, a * 10 + i);
            st[i] = false;
        }
}

int main()
{
    cin >> n;

    dfs_a(0, 0);

    cout << ans << endl;

    return 0;
}