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| #include<stdio.h> #include<set> #include<iostream> #include<stack> #include<cstring> #include<cmath> #include<vector> #include<map> #include<queue> #include<algorithm> typedef long long ll; typedef long double ld; typedef double db; #define io_opt ios::sync_with_stdio(false);cin.tie(0);cout.tie(0) using namespace std; const int mod=998244353; ll mo(ll a,ll p){ return a>=p?a%p:a; } inline int rd() { int x = 0, f = 1; char ch; while (ch < '0' || ch > '9') { if (ch == '-')f = -1; ch = getchar(); } while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); } return f * x; } inline ll gcd(ll x, ll y){ return y==0?x:gcd(y,x%y); } inline ll speed(ll a,ll b){ ll cur=a,anss=1; while(b){ if(b&1) anss=anss*cur; cur=cur*cur; b>>=1; } return anss; } const int MAXN=1e5; bool ipr[MAXN+20]; int cnt,pri[MAXN/5]; void prime(){ int N=sqrt(MAXN)+0.5,mul; memset(ipr,true,sizeof(ipr)); ipr[1]=false; for(int i=2;i<=N;i++){ if(ipr[i]==true){ i==2?mul=1:mul=2; for(int j=i*i;j<=MAXN;j+=i*mul){ ipr[j]=false; } } } for(int i=2;i<=MAXN;i++){ if(ipr[i]==true){ pri[++cnt]=i; } } } int T,a,b; int wei(int x){ int ret=0; do{ x/=10; ret++; }while(x); return ret; } struct E{ int num,cnt; }; bool f[100020]; int bits[10]; int comb(int t){ int ret=0; for(int i=t;i>=1;i--){ ret*=10; ret+=bits[i]; } return ret; } int bfs(){ int t=wei(a); queue<E>q; q.push((E){a,0}); f[a]=true; while(!q.empty()){ E cur=q.front();q.pop(); if(cur.num==b) return cur.cnt; for(int i=1;i<=t;i++){ bits[i]=cur.num%10; cur.num/=10; } for(int i=1;i<=t;i++){ int d=bits[i]; for(int j=0;j<=9;j++){ if(j==d||(i==t&&j==0)) continue; bits[i]=j; int nex=comb(t); if(ipr[nex]&&!f[nex]){ f[nex]=true; q.push((E){nex,cur.cnt+1}); } } bits[i]=d; } } return -1; } int main(){ io_opt; prime(); cin>>T; while(T--){ memset(f,false,sizeof(f)); cin>>a>>b; if(a==b){ cout<<0<<endl; continue; } int ans=bfs(); if(ans==-1){ cout<<"No solution"<<endl; } else{ cout<<ans<<endl; } } return 0; }
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