POJ3982 序列

/* POJ3982 序列 */

#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>

using namespace std;

/* 无符号整数类，整数放在字符串中，可以用整数初始化。
* 只有以下功能：
* 1.数组
* 2.加运算。
*/
class UBigInt {
private:
string num;
public:
UBigInt();
UBigInt(int n);
void setNumber(string s);
const string& getNumber(); // retrieves the number
UBigInt operator + (UBigInt b);
private:
string add(string number1, string number2);
UBigInt& operator [] (int n);
};

UBigInt::UBigInt() { // empty constructor initializes zero
num = "0";
}

UBigInt::UBigInt(int n) {
stringstream ss;
string s;
ss << n;
ss >> s;
setNumber(s);
}

void UBigInt::setNumber(string s) {
num = s;
}

const string& UBigInt::getNumber() { // retrieves the number
return num;
}

UBigInt UBigInt::operator + (UBigInt b) {
UBigInt addition;
addition.setNumber( add(getNumber(), b.getNumber() ) );

return addition;
}

string UBigInt::add(string number1, string number2) {
string add = (number1.length() > number2.length()) ?  number1 : number2;

int diffLength = abs( (int) (number1.size() - number2.size()) );
if(number1.size() > number2.size())
number2.insert(0, diffLength, '0'); // put zeros from left
else// if(number1.size() < number2.size())
number1.insert(0, diffLength, '0');

char carry = 0;
for(int i=number1.size()-1; i>=0; --i) {
add[i] = (carry+(number1[i]-'0')+(number2[i]-'0')) + '0';

if(i != 0) {
if(add[i] > '9') {
add[i] -= 10;
carry = 1;
} else
carry = 0;
}
}
if(add[0] > '9') {
add[0]-= 10;
add.insert(0,1,'1');
}
return add;
}

UBigInt& UBigInt::operator [] (int n) {
return *(this + (n*sizeof(UBigInt)));
}

int main()
{
UBigInt t[99+1];
int a, b, c;

while(scanf("%d%d%d", &a, &b, &c) != EOF) {
t[0] = a;
t[1] = b;
t[2] = c;

for(int i=3; i<=99; i++)
t[i] = t[i-3] + t[i-2] + t[i-1];

cout << t[99].getNumber() << endl;
}

return 0;
}