Codeforces Round #209 (Div. 2)C

刷了一页的WA  。。终于发现了 哪里错了 快速幂模板里一个变量t居然开得long  ...

虽然代码写的丑了点 但是是对的 那个该死的long 啊..

#include <iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<stdlib.h>
#include<vector>
using namespace std;
#define mod 1000000007
#define LL __int64
#define N 100010
LL n,x,a[N],s,b[N];
LL exp_mod(LL a,LL n,LL b)
{
    long long t;
    if(n==0) return 1%b;
    if(n==1) return a%b;
    t=exp_mod(a,n/2,b);
    t=t*t%b;
    if((n&1)==1) t=t*a%b;
    return t;
}
int main()
{
    int i;
    cin>>n>>x;
    for(i = 1; i <= n ; i++)
    {
        scanf("%I64d",&a[i]);
        s = s+a[i];
        b[i] = a[i];
    }
    for(i = 1; i <= n ; i++)
    {
        b[i] = s-a[n-i+1];
    }
    for(i = 1; i <= n ;i++)
    a[i] = b[i];
    LL k = a[1];
    int o = 2;LL ss=a[1];
    LL sum=1;
    b[2]-=a[1];
    while(1)
    {
        if(b[o]==0&&o<=n)
        {
            o++;
            b[o]-=a[o-1];
            sum++;
            if(o>n) break;
            else
            continue;
        }
        if(o>n) break;
        if(sum%x!=0) break;
        while(sum%x==0&&o<=n)
        {
            sum/=x;
            ss++;
            b[o]--;
            if(b[o]==0)
            {
                o++;
                b[o]-=a[o-1];
                sum++;
                break;
            }
        }
        if(o>n) break;
    }
    while(sum&&sum%x==0)
    {
        ss+=1;
        sum/=x;
    }
    printf("%I64d
",exp_mod(x,min(s,ss),mod));
    return 0;
}