参考 http://www.cnblogs.com/studynote/p/3445398.html
#include <iostream>
#include <time.h>using namespace std;class BigInt {
public://BigInt();BigInt(const char*);BigInt(unsigned int n = 0);BigInt(const BigInt&);BigInt& operator=(const BigInt&);BigInt operator + (const BigInt& other) const;void print(FILE* F = stdout) const;~BigInt() {delete[] digits;}
private:char* digits;unsigned ndigits;BigInt(char* d, unsigned n) {digits = d;ndigits = n;}friend class DigitStream;
};void BigInt::print(FILE *f) const {for (int i = ndigits - 1; i >= 0; --i) {fprintf(f, "%c", digits[i] + '0');}
}BigInt::BigInt(const BigInt& n) {unsigned i = n.ndigits;digits = new char[i];ndigits = i;memcpy(digits, n.digits, i);
}BigInt& BigInt::operator=(const BigInt& n) {if (this != &n) {BigInt tmp(n);swap(tmp.ndigits, ndigits);swap(tmp.digits, digits);}return *this;
}BigInt::BigInt(unsigned n) {char d[3 * sizeof(unsigned) + 1];char *dp = d;ndigits = 0;do {*dp++ = n % 10;n /= 10;ndigits++;} while (n > 0);digits = new char[ndigits];for (register int i = 0; i < ndigits; ++i) {digits[i] = d[i];}
}BigInt::BigInt(const char* digitString) {size_t n = strlen(digitString);if (n != 0) {ndigits = n;digits = new char[n];for (int i = 0; i < n; ++i) {digits[i] = digitString[n - 1 - i] - '0';}}else {ndigits = 1;digits = new char[ndigits];digits[0] = 0;}
}BigInt BigInt::operator+(const BigInt& n) const {size_t maxDigits = max(ndigits, n.ndigits) + 1;char carry = 0;char* sumPtr = new char[maxDigits];BigInt sum(sumPtr, maxDigits);for (int i = 0; i < max(ndigits, n.ndigits); ++i) {*sumPtr = carry;if (i < ndigits) {char tmp = digits[i];*sumPtr += digits[i];tmp = *sumPtr;int a = 0;}if (i < n.ndigits) {char tmp = digits[i];*sumPtr += n.digits[i];tmp = *sumPtr;int a = 0;}if (*sumPtr >= 10) {carry = 1;*sumPtr -= 10;}else {carry = 0;}++sumPtr;}if (carry > 0) {*sumPtr = carry;}else {sum.ndigits = max(ndigits, n.ndigits);}return sum;
}void test() {clock_t start = clock();BigInt b(10);for (int i = 1; i <= 1; ++i) {b = b + 1;}b.print();clock_t end = clock();cout << endl << static_cast<double>(end - start) / CLOCKS_PER_SEC << endl;
}int main(int argc, _TCHAR* argv[])
{test();_CrtDumpMemoryLeaks();cin.get();return 0;
}