uva 10624 Super Number 回溯

  暴力回溯，用位运算加个奇偶剪枝

  注意取余的效率，因为取余实在太慢了，所以要最少的进行取余运算，所以就是每19位进行次取余，这样1s内就过了

/*author:jxylang:C/C++university:China,Xidian University**If you need to reprint,please indicate the source***/#include <stdio.h>int ans[50];char nok(int now){    int i,t;    unsigned long long r;    for(i=r=t=0;i<now;i++,t++)    {        r=r*10+ans[i];        if(t==18)//19位        {            t=0;            r%=now;        }    }    return r%now;}int n,m;char dfs(int now){    if(now>m)return 1;    int i=(now==1),f=now&1,t=now-1;    for(;i<10;i++)    {        ans[t]=i;        if(now>=n&&((!f&&(i&1))||nok(now)))continue;//奇偶        if(dfs(now+1))return 1;    }    return 0;}int main(){    int T,C=0;    scanf("%d",&T);    while(T--)    {        scanf("%d%d",&n,&m);        printf("Case %d: ",++C);        if(!dfs(1))printf("-1\n");        else        {            int i;            for(i=0;i<m;i++)               printf("%d",ans[i]);            puts("");        }    }}