hdu 5936 2016ccpc 杭州 - D

数学题好难啊！！！！

最长长度不超过十位， 折半枚举。。。

题解

 #include<bits/stdc++.h>
 #define LL long long
 #define fi first
 #define se second
 #define mk make_pair
 #define pii pair<int,int>
 #define piii pair<int, pair<int,int>>

 using namespace std;

 const int N = 1e5 + ;
 const int M = 1e4 + ;
 const int inf = 0x3f3f3f3f;
 const LL INF = 0x3f3f3f3f3f3f3f3f;
 const LL base = ;
 const int mod = 1e9 + ;

 int x, k;
 LL f[N][], v[N];

 int fastPow(int a, int b) {
     int ans = ;
     while(b) {
         if(b & ) ans = ans * a;
         a = a * a; b >>= ;
     }
     return ans;
 }
 void init() {
     for(int i = ; i < N; i++) {
         for(int j = ; j < ; j++) {
             for(int now = i; now; now /= ) {
                 f[i][j] += fastPow(now % , j);
             }
         }
     }
 }

 int main() {
     init();
     int T; scanf("%d", &T);
     for(int cas = ; cas <= T; cas++) {
         scanf("%d%d", &x, &k);
         LL ans = ;
         for(int i = ; i < base; i++)
             v[i] = f[i][k] - i * base;
         sort(v, v + base);

         for(int i = ; i < base; i++) {
             LL ret = f[i][k] - i;
             ans += upper_bound(v, v + base, x - ret) - lower_bound(v, v + base, x - ret);
         }

         ans -= (x == );
         printf("Case #%d: ", cas);
         printf("%lld\n", ans);
     }
     return ;
 }
 /*
 */