SPOJ 362 Ignore the Garbage 转7进制+简单大数除法

显然正着倒着看仍然是数字的只有7个数：0,1,2,5,6,8,9

所以就是用这7个数组合成不同的数。

将n转换成7进制，对应位输出即可。

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>

using namespace std;

const char num[] = "0125986";
const int MAXN = 1010;
const int BASE = 7;

char str[MAXN];
int a[MAXN];
int b[MAXN];
int ans[MAXN];
int cnt, len;

bool check()
{
    for ( int i = 0; i < len; ++i )
        if ( a[i] ) return true;
    return false;
}

void Mod()
{
    int tmp = 0;
    for ( int i = 0; i < len; ++i )
    {
        tmp = tmp * 10 + a[i];
        b[i] = tmp / BASE;
        tmp %= BASE;
    }
    ans[cnt++] = tmp;

    int i = 0, j;
    while ( i < len && b[i] == 0 ) ++i;
    for ( j = 0; i < len; ++i, ++j )
        a[j] = b[i];
    len = j;

    return;
}

int main()
{
    int T;
    scanf( "%d", &T );
    while ( T-- )
    {
        scanf( "%s", str );
        len = strlen(str);
        cnt = 0;
        for ( int i = 0; i < len; ++i )
            a[i] = str[i] - '0';

        while ( check() ) Mod();

        for ( int i = 0; i < cnt; ++i )
            putchar( num[ ans[i] ] );

        puts("");
    }
    return 0;
}