cf 359C

stl 里的map使用   然后就是快速幂取余

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#include <map>
#define LL long long
#define mod 1000000007
using namespace std;
LL num[100010];
LL pow_mod(LL a, LL n)
{
    if(n == 0)
        return 1;
    LL x = pow_mod(a, n/2);
    LL ans = (LL)x*x%mod;
    if(n%2) ans = ans*a%mod;
    return ans;
}
int main()
{
    LL n, x, _max, sum = 0;
    scanf("%I64d%I64d",&n,&x);
    for(int i = 0; i < n; i++)
    {
        scanf("%I64d",&num[i]);
        sum += num[i];
    }
    _max = sum;
    for(int i = 0; i < n; i++)
    {
        num[i] = sum-num[i];
        _max = min(_max, num[i]);
    }
    map<LL, int> g;
    for(int i = 0; i < n; i++)
    {
        num[i] -= _max;
        g[num[i]]++;
    }
    int r = 0;
    for (int i = 0; ; i++)
    {
        r += g[i];
        if (r % x || r == 0)
            break;
        r /= x;
        _max++;
    }
    if(_max > sum)
        _max = sum;
    printf("%I64d\n",pow_mod(x%mod, _max));
    return 0;
}