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

 1 #include<bits/stdc++.h>
 2 #define LL long long
 3 #define fi first
 4 #define se second
 5 #define mk make_pair
 6 #define pii pair<int,int>
 7 #define piii pair<int, pair<int,int>>
 8 
 9 using namespace std;
10 
11 const int N = 1e5 + 7;
12 const int M = 1e4 + 7;
13 const int inf = 0x3f3f3f3f;
14 const LL INF = 0x3f3f3f3f3f3f3f3f;
15 const LL base = 100000;
16 const int mod = 1e9 + 7;
17 
18 int x, k;
19 LL f[N][10], v[N];
20 
21 int fastPow(int a, int b) {
22     int ans = 1;
23     while(b) {
24         if(b & 1) ans = ans * a;
25         a = a * a; b >>= 1;
26     }
27     return ans;
28 }
29 void init() {
30     for(int i = 0; i < N; i++) {
31         for(int j = 0; j < 10; j++) {
32             for(int now = i; now; now /= 10) {
33                 f[i][j] += fastPow(now % 10, j);
34             }
35         }
36     }
37 }
38 
39 
40 int main() {
41     init();
42     int T; scanf("%d", &T);
43     for(int cas = 1; cas <= T; cas++) {
44         scanf("%d%d", &x, &k);
45         LL ans = 0;
46         for(int i = 0; i < base; i++)
47             v[i] = f[i][k] - i * base;
48         sort(v, v + base);
49 
50         for(int i = 0; i < base; i++) {
51             LL ret = f[i][k] - i;
52             ans += upper_bound(v, v + base, x - ret) - lower_bound(v, v + base, x - ret);
53         }
54 
55         ans -= (x == 0);
56         printf("Case #%d: ", cas);
57         printf("%lld\n", ans);
58     }
59     return 0;
60 }
61 /*
62 */