HDU 5047 Sawtooth(有趣的思维题+证明)
Sawtooth
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 979 Accepted Submission(s): 375
Problem Description
Think about a plane:
● One straight line can divide a plane into two regions.
● Two lines can divide a plane into at most four regions.
● Three lines can divide a plane into at most seven regions.
● And so on...
Now we have some figure constructed with two parallel rays in the same direction, joined by two straight segments. It looks like a character “M”. You are given N such “M”s. What is the maximum number of regions that these “M”s can divide a plane ?
● One straight line can divide a plane into two regions.
● Two lines can divide a plane into at most four regions.
● Three lines can divide a plane into at most seven regions.
● And so on...
Now we have some figure constructed with two parallel rays in the same direction, joined by two straight segments. It looks like a character “M”. You are given N such “M”s. What is the maximum number of regions that these “M”s can divide a plane ?
Input
The first line of the input is T (1 ≤ T ≤ 100000), which stands for the number of test cases you need to solve.
Each case contains one single non-negative integer, indicating number of “M”s. (0 ≤ N ≤ 10 12)
Each case contains one single non-negative integer, indicating number of “M”s. (0 ≤ N ≤ 10 12)
Output
For each test case, print a line “Case #t: ”(without quotes, t means the index of the test case) at the beginning. Then an integer that is the maximum number of regions N the “M” figures can divide.
Sample Input
2 1 2
Sample Output
Case #1: 2 Case #2: 19
题意：n个M型（有两条要平行），最多能将整个空间分成多少份。
思路：首先考虑简单的情况：即n条直线最多能将空间分成多少份，用L（n）来表示
L(0) = 1，L(1) = 2,L(2) = 4,L(3) = 7........
很容易想到，求L(n)时，这一条直线最多与n-1条直线有n-1个交点,增加了n个区域（对n个已有区域进行了划分）因此递推式就为：
L(n) = L(n-1)+n
可以得到L(n) = (n+1)*n/2+1
再过来看M型：
如果把一个M型看成4条直线（两条边平行），那么我们可以直接通过刚才那个式子得到答案！
但是，它是射线！如果尝试着把线段无限延长，就会发现其实你可以把这个M型看成是4条直线划分空间但是有些空间是浪费的（这些浪费的空间都是在那三个头），而且可以算出损失的空间数为9，但是容易想到你想要划分的空间最大，就是要让每个M型的三个头都露在外面！（贪心）这样的话，因此每个M型的三个头都露在外面，因此可以得到公式
M(n) = L(4*n)-9*n = 8n^2-7n+1
另外，如果两边边不平行，结果也是一样的 ！
代码细节优化就没啥意思了。。。
#include
#include
#include
using namespace std;
#define MAXN 9999
#define MAXSIZE 1010
#define DLEN 4
class BigNum
{
private:
int a[500]; //可以控制大数的位数
int len;
public:
BigNum()
{
len=1; //构造函数
memset(a,0,sizeof(a));
}
BigNum(const long long); //将一个int类型的变量转化成大数
BigNum(const char*); //将一个字符串类型的变量转化为大数
BigNum(const BigNum &); //拷贝构造函数
BigNum &operator=(const BigNum &); //重载赋值运算符，大数之间进行赋值运算
friend istream& operator>>(istream&,BigNum&); //重载输入运算符
friend ostream& operator<<(ostream&,BigNum&); //重载输出运算符
BigNum operator+(const BigNum &)const; //重载加法运算符，两个大数之间的相加运算
BigNum operator-(const BigNum &)const; //重载减法运算符，两个大数之间的相减运算
BigNum operator*(const BigNum &)const; //重载乘法运算符，两个大数之间的相乘运算
BigNum operator/(const int &)const; //重载除法运算符，大数对一个整数进行相除运算
BigNum operator^(const int &)const; //大数的n次方运算
int operator%(const int &)const; //大数对一个int类型的变量进行取模运算
bool operator>(const BigNum &T)const; //大数和另一个大数的大小比较
bool operator>(const int &t)const; //大数和一个int类型的变量的大小比较
void print(); //输出大数
};
BigNum::BigNum(const long long b) //将一个int类型的变量转化为大数
{
long long c,d=b;
len=0;
memset(a,0,sizeof(a));
while(d>MAXN)
{
c=d-(d/(MAXN+1))*(MAXN+1);
d=d/(MAXN+1);
a[len++]=c;
}
a[len++]=d;
}
BigNum::BigNum(const char *s) //将一个字符串类型的变量转化为大数
{
int t,k,index,L,i;
memset(a,0,sizeof(a));
L=strlen(s);
len=L/DLEN;
if(L%DLEN)len++;
index=0;
for(i=L-1; i>=0; i-=DLEN)
{
t=0;
k=i-DLEN+1;
if(k<0)k=0;
for(int j=k; j<=i; j++)
t=t*10+s[j]-'0';
a[index++]=t;
}
}
BigNum::BigNum(const BigNum &T):len(T.len) //拷贝构造函数
{
int i;
memset(a,0,sizeof(a));
for(i=0; i>(istream &in,BigNum &b)
{
char ch[MAXSIZE*4];
int i=-1;
in>>ch;
int L=strlen(ch);
int count=0,sum=0;
for(i=L-1; i>=0;)
{
sum=0;
int t=1;
for(int j=0; j<4&&i>=0; j++,i--,t*=10)
{
sum+=(ch[i]-'0')*t;
}
b.a[count]=sum;
count++;
}
b.len=count++;
return in;
}
ostream& operator<<(ostream& out,BigNum& b) //重载输出运算符
{
int i;
cout<=0; i--)
{
printf("%04d",b.a[i]);
}
return out;
}
BigNum BigNum::operator+(const BigNum &T)const //两个大数之间的相加运算
{
BigNum t(*this);
int i,big;
big=T.len>len?T.len:len;
for(i=0; iMAXN)
{
t.a[i+1]++;
t.a[i]-=MAXN+1;
}
}
if(t.a[big]!=0)
t.len=big+1;
else t.len=big;
return t;
}
BigNum BigNum::operator-(const BigNum &T)const //两个大数之间的相减运算
{
int i,j,big;
bool flag;
BigNum t1,t2;
if(*this>T)
{
t1=*this;
t2=T;
flag=0;
}
else
{
t1=T;
t2=*this;
flag=1;
}
big=t1.len;
for(i=0; ii)
t1.a[j--]+=MAXN;
t1.a[i]+=MAXN+1-t2.a[i];
}
else t1.a[i]-=t2.a[i];
}
t1.len=big;
while(t1.a[len-1]==0 && t1.len>1)
{
t1.len--;
big--;
}
if(flag)
t1.a[big-1]=0-t1.a[big-1];
return t1;
}
BigNum BigNum::operator*(const BigNum &T)const //两个大数之间的相乘
{
BigNum ret;
int i,j,up;
int temp,temp1;
for(i=0; iMAXN)
{
temp1=temp-temp/(MAXN+1)*(MAXN+1);
up=temp/(MAXN+1);
ret.a[i+j]=temp1;
}
else
{
up=0;
ret.a[i+j]=temp;
}
}
if(up!=0)
ret.a[i+j]=up;
}
ret.len=i+j;
while(ret.a[ret.len-1]==0 && ret.len>1)ret.len--;
return ret;
}
BigNum BigNum::operator/(const int &b)const //大数对一个整数进行相除运算
{
BigNum ret;
int i,down=0;
for(i=len-1; i>=0; i--)
{
ret.a[i]=(a[i]+down*(MAXN+1))/b;
down=a[i]+down*(MAXN+1)-ret.a[i]*b;
}
ret.len=len;
while(ret.a[ret.len-1]==0 && ret.len>1)
ret.len--;
return ret;
}
int BigNum::operator%(const int &b)const //大数对一个 int类型的变量进行取模
{
int i,d=0;
for(i=len-1; i>=0; i--)
d=((d*(MAXN+1))%b+a[i])%b;
return d;
}
bool BigNum::operator>(const BigNum &T)const //大数和另一个大数的大小比较
{
int ln;
if(len>T.len)return true;
else if(len==T.len)
{
ln=len-1;
while(a[ln]==T.a[ln]&&ln>=0)
ln--;
if(ln>=0 && a[ln]>T.a[ln])
return true;
else
return false;
}
else
return false;
}
bool BigNum::operator>(const int &t)const //大数和一个int类型的变量的大小比较
{
BigNum b(t);
return *this>b;
}
void BigNum::print() //输出大数
{
int i;
printf("%d",a[len-1]);
for(i=len-2; i>=0; i--)
printf("%04d",a[i]);
printf("\n");
}
int main()
{
int ncase,T=1;
cin >> ncase;
while(ncase--)
{
long long t;
scanf("%I64d",&t);
if(t <= 1e9)
{
printf("Case #%d: %I64d\n",T++,8*t*t-7*t+1);
}
else
{
BigNum tmp = BigNum(t);
printf("Case #%d: ",T++);
tmp = (tmp*tmp*8-tmp*7+1);
tmp.print();
}
}
return 0;
}