hdu 5936 2016ccpc 杭州

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 + 7;
const int M = 1e4 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const LL base = 100000;
const int mod = 1e9 + 7;

int x, k;
LL f[N][10], v[N];

int fastPow(int a, int b) {
    int ans = 1;
    while(b) {
        if(b & 1) ans = ans * a;
        a = a * a; b >>= 1;
    }
    return ans;
}
void init() {
    for(int i = 0; i < N; i++) {
        for(int j = 0; j < 10; j++) {
            for(int now = i; now; now /= 10) {
                f[i][j] += fastPow(now % 10, j);
            }
        }
    }
}


int main() {
    init();
    int T; scanf("%d", &T);
    for(int cas = 1; cas <= T; cas++) {
        scanf("%d%d", &x, &k);
        LL ans = 0;
        for(int i = 0; i < base; i++)
            v[i] = f[i][k] - i * base;
        sort(v, v + base);

        for(int i = 0; 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 == 0);
        printf("Case #%d: ", cas);
        printf("%lld
", ans);
    }
    return 0;
}
/*
*/