% mod 比较基本的广搜 有些数论知识 第一次在节点力用了队列 挺好 #include<iostream> #include<queue> using namespace std; struct Node { int x; int step; queue<char> q; }; int v[1000010]; int n,m,k; bool bfs() { int s=((n+1)%k+k)%k; queue<Node>q; Node now,next; now.x=n;now.step=0; q.push(now); memset(v,0,sizeof(v)); while(!q.empty()) { now=q.front(); if((now.x%k+k)%k==s) { printf("%d ",now.step); while(now.step--) { printf("%c",now.q.front()); now.q.pop(); } printf(" "); return true; } q.pop(); int xx; xx=(now.x+m)%(k*m); if(!v[(xx%k+k)%k]) { v[(xx%k+k)%k]=1; next=now;next.x=xx;next.q.push('+');next.step++; q.push(next); } xx=(now.x-m)%(k*m); if(!v[(xx%k+k)%k]) { v[(xx%k+k)%k]=1; next=now;next.x=xx;next.q.push('-');next.step++; q.push(next); } xx=(now.x*m)%(k*m); if(!v[(xx%k+k)%k]) { v[(xx%k+k)%k]=1; next=now;next.x=xx;next.q.push('*');next.step++; q.push(next); } xx=((now.x%m+m)%m)%(m*k); if(!v[(xx%k+k)%k]) {v[(xx%k+k)%k]=1; next=now;next.x=xx;next.q.push('%');next.step++; q.push(next); } } return 0; } int main() { while(scanf("%d%d%d",&n,&k,&m)!=EOF) { if(n==0&&k==0&&m==0) break; if(!bfs()) printf("0 "); } return 0; }