poj1023

二进制相关问题，构造

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#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;

#define LL long long
#define maxn 100

int n;
LL m;
char st[maxn];
int f[maxn];
int g[maxn];

bool work()
{
    memset(f, 0, sizeof(f));
    memset(g, 0, sizeof(g));
    for (int i = 0; i < n; i++)
        f[i] = (m >> i) & 1;
    for (int i = 0; i < n; i++)
    {
        if (!f[i])
        {
            g[i] = 0;
            continue;
        }
        if (f[i] && st[i] == 'p')
        {
            g[i] = 1;
            continue;
        }
        g[i] = 1;
        i++;
        while (i < n && !(st[i] == 'p' && f[i] == 0))
        {
            if (f[i])
                g[i] = 0;
            else
                g[i] = 1;
            i++;
        }
        if (i >= n)
            return false;
        g[i] = 1;
    }
    return true;
}

void print()
{
    for (int i = n - 1; i >= 0; i--)
        putchar('0' + g[i]);
    putchar('\n');
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%d", &n);
        scanf("%s", st);
        reverse(st, st + n);
        scanf("%lld", &m);
        if (m < 0)
        {
            for (int i = 0; i < n; i++)
                if (st[i] == 'p')
                    st[i] = 'n';
                else
                    st[i] = 'p';
            m =-m;
        }
        if (!work())
            printf("Impossible\n");
        else
            print();
    }
    return 0;
}