HDU 1104 Remainder

156ms,比其他人慢好多。。

bfs暴搜

#include<cstdio>
#include<iostream>
#include<cstring>
#include<queue>
using namespace std;

const int maxN=2000010;
int n,k,m,step;
bool vis[maxN];
string anstr;
struct Node{
    int n,k;
    string str;
}no;
queue<Node> q;

void push(int tn,char c){
    if(c=='%'&&tn<0) tn+=m; 
    tn%=(m*k);
    Node nn;
    nn.n=tn;nn.k=no.k+1;nn.str=no.str+c;
    if(!vis[tn+m*k]) q.push(nn);
    vis[tn+m*k]=true;
}
void bfs(){
    while(!q.empty()) q.pop();
    no.n=n;no.str="";no.k=0;
    q.push(no);
    int tar=(n+1)%k;
    if(tar<0) tar+=k;
    while(!q.empty()){
        no=q.front();q.pop();
        int cur=no.n%k;
        //cout<<no.n<<endl;
        if(cur<0) cur+=k;
        if(tar==cur){
            step=no.k;
            anstr=no.str;
            return;
        }
        push(no.n+m,'+');
        push(no.n-m,'-');
        push(no.n*m,'*');
        push(no.n%m,'%');
    }
}
int main(){
    while(cin>>n>>k>>m,n||k||m){
        memset(vis,false,sizeof(vis));
        step=0;
        bfs();
        cout<<step<<endl;
        if(step) cout<<anstr<<endl;
    }
    return 0;
}