生日蛋糕 POJ - 1190 搜索 数学

http://poj.org/problem?id=1190

题解：四个剪枝。

#define _CRT_SECURE_NO_WARNINGS
#include<cstring>
#include<cctype>
#include<cstdlib>
#include<cmath>
#include<cstdio>
#include<string>
#include<stack>
#include<ctime>
#include<list>
#include<set>
#include<map>
#include<queue>
#include<vector>
#include<sstream>
#include<iostream>
#include<functional>
#include<algorithm>
#include<memory.h>
//#define INF 0x3f3f3f3f
#define eps 1e-6
#define pi acos(-1.0)
#define e exp(1.0)
#define rep(i,t,n)  for(int i =(t);i<=(n);++i)
#define per(i,n,t)  for(int i =(n);i>=(t);--i)
#define mp make_pair
#define pb push_back
#define mmm(a,b) memset(a,b,sizeof(a))
//std::ios::sync_with_stdio(false);
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
void smain();
#define ONLINE_JUDGE
int main() {
//    ios::sync_with_stdio(false);
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    long _begin_time = clock();
#endif
    smain();
#ifndef ONLINE_JUDGE
    long _end_time = clock();
    printf("time = %ld ms.", _end_time - _begin_time);
#endif
    return ;
}
int n, m;
int mn =  << ;
int area = ;
int mnV[];
int mnA[];
int maxVforNRH(int n, int r, int h) {
    int v = ;
    rep(i, , n - )
        v += (r - i)*(r - i)*(h - i);
        return v;

}
void  dfs(int v,int n,int r,int h) {//n层凑v，底层不超r，h
    if (n == ) {
        if (v)return;
        else {
            mn = min(mn, area);
            return;
        }
    }
    if (v <= )return;
    if (mnV[n] > v)return;//
    if (area + mnA[n] >= mn)return;//
    if (h < n || r < n)return; //
    if (maxVforNRH(n,r,h)< v)return;//
    per(rr, r, n) {
        if (n == m)area = rr*rr;
        per(hh, h, n) {
            area +=  * rr*hh;
            dfs(v - rr*rr*hh, n - , rr - , hh - );
            area -=  * rr*hh;
        }
    }
}
void Run() {

}

void smain() {

    cin >> n >> m;
    mnV[] = ;
    mnA[] = ;
    rep(i, , m) {
        mnV[i] = mnV[i - ] + i*i*i;
        mnA[i] = mnA[i - ] +  * i*i;
    }
    if (mnV[m] > n)cout <<  << endl;
    else {
        int maxH = (n - mnV[m - ]) / (m*m) + ;
        int maxR = sqrt(double(n - mnV[m - ]) / m) + ;//底层最大的H，R
        area = ;
        mn =  << ;
        dfs(n, m, maxH, maxR);
        if (mn ==  << ) {
            cout <<  << endl;

        }
        else cout << mn << endl;
    }
    Run();
}