Codeforces Round #107 (Div. 2)

D题

并查集+组合

#include <iostream>

#include <cstdio>

#include <cstring>

using namespace std;

#define MOD 1000000007

int o[2001];

int find(int x)

{

    int t,r;

    t = x;

    while(x != o[x])

    x = o[x];

    while(x != t)

    {

        r = o[t];

        o[t] = x;

        t = r;

    }

    return x;

}

void merge(int x,int y)

{

    x = find(x);

    y = find(y);

    if(x != y)

    o[x] = y;

}

int main()

{

    int i,j,n,m,k,ans = 0;

    scanf("%d%d%d",&n,&m,&k);

    for(i = 1;i <= n;i ++)

    o[i] = i;

    for(i = 1;i <= n;i ++)

    {

        if(k%2 == 0)

        {

            if(2*i < k) continue;

            if(i + k/2 > n) continue;

            for(j = 0;j < k/2;j ++)

            {

                merge(i-j,i+1+j);

            }

        }

        else

        {

            if(2*i-1 < k) continue;

            if(i + k/2 > n) continue;

            for(j = 0;j < k/2;j ++)

            merge(i-1-j,i+1+j);

        }

    }

    for(i = 1;i <= n;i ++)

    {

        if(find(i) == i)

        ans ++;

    }

    int sd = 1;

    for(i = 1;i <= ans;i ++)

    sd = ((__int64)sd*m)%MOD;

    printf("%d\n",sd);

    return 0;

}

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