Factorial for any number

problem1

/* 
 * File:   main.cpp
 * Author: mihiranad
 *
 * Created on August 28, 2014, 12:18 PM
 */

#include <cstdlib>
#include <cstring>
#include <iostream>
#include <cmath>
#include <list>
#include <assert.h>    
#include <boost/lexical_cast.hpp>

using namespace std;

int stringToInt(std::string num) {

    int number;
    try {
        number = boost::lexical_cast<int>(num);
    } catch (boost::bad_lexical_cast&) {
        number = -1;
    }
    return number;

}

int charToInt(char num) {

    int number;
    try {
        number = boost::lexical_cast<int>(num);
    } catch (boost::bad_lexical_cast&) {
        number = -1;
    }
    return number;

}

std::string intToString(unsigned int num) {

    std::string number;
    try {
        number = boost::lexical_cast<std::string>(num);
    } catch (boost::bad_lexical_cast&) {
        number = -1;
    }
    return number;

}

void printArr(const unsigned int* arr, const unsigned int len) {

    for (int i = 0; i < len; i++)
        std::cout << arr[i];
    std::cout << std::endl;

}

void addToIndex(unsigned int* pArr, unsigned int index, unsigned int number) {

    unsigned int val = pArr[index] + number;
    unsigned int res = val % 10;
    unsigned int carry = val / 10;
    pArr[index] = res;

    if (carry == 0) {
        return;
    } else
        addToIndex(pArr, index - 1, carry);

}

std::string multiply(std::string num1, std::string num2) {

    unsigned int uiNum1Len = num1.length();
    unsigned int uiNum2Len = num2.length();

    int *pNum1Arr = new int[uiNum1Len];
    int *pNum2Arr = new int[uiNum2Len];

    for (int i = 0; i < uiNum1Len; i++)
        pNum1Arr[i] = charToInt(num1[i]);
    for (int i = 0; i < uiNum2Len; i++)
        pNum2Arr[i] = charToInt(num2[i]);

    unsigned int uiResLen = uiNum1Len + uiNum2Len;
    unsigned int *pRes = new unsigned int[uiResLen];
    for (int i = 0; i < uiResLen; i++)
        pRes[i] = 0;

    unsigned int uiIndex = uiResLen - 1;
    unsigned int uiInternalIndex;
    for (int i = (uiNum1Len - 1); i >= 0; i--) {
        uiInternalIndex = uiIndex--;
        unsigned int digit1 = pNum1Arr[i];
        for (int j = (uiNum2Len - 1); j >= 0; j--) {
            unsigned int digit2 = pNum2Arr[j];
            unsigned int res = digit1 * digit2;
            addToIndex(pRes, uiInternalIndex, res);
            uiInternalIndex--;
        }
    }

    std::string sRes;
    for (int i = 0; i < uiResLen; i++)
        sRes.append(intToString(pRes[i]));

    //printArr(pRes, uiNum1Len + uiNum2Len);
    return sRes;

}

std::string add(std::string num1, std::string num2) {

    if (num1.size() < num2.size()) {
        while (num1.size() < num2.size())
            num1 = "0" + num1;
    } else if (num2.size() < num1.size()) {
        while (num2.size() < num1.size())
            num2 = "0" + num2;
    }

    unsigned int uiLen = num1.length();

    int *pNum1Arr = new int[uiLen];
    int *pNum2Arr = new int[uiLen];

    for (int i = 0; i < uiLen; i++) {
        pNum1Arr[i] = charToInt(num1[i]);
        pNum2Arr[i] = charToInt(num2[i]);
    }

    unsigned int uiResLen = uiLen + 1;
    unsigned int *pRes = new unsigned int[uiResLen];
    for (int i = 0; i < uiResLen; i++)
        pRes[i] = 0;

    unsigned int uiIndex = uiResLen - 1;
    for (int i = uiLen - 1; i >= 0; i--) {
        unsigned int digit1 = pNum1Arr[i];
        unsigned int digit2 = pNum2Arr[i];
        unsigned int res = digit1 + digit2;
        addToIndex(pRes, uiIndex, res);
        uiIndex--;
    }

    //    printArr(pRes, uiResLen);
    //    std::cout << num1 << std::endl;
    //    std::cout << num2 << std::endl;

    std::string sRes;
    for (int i = 0; i < uiResLen; i++)
        sRes.append(intToString(pRes[i]));

    //printArr(pRes, uiNum1Len + uiNum2Len);
    return sRes;

}

std::string factorial(unsigned int num) {

    if (num == 1)
        return "1";

    std::string sNum = intToString(num);
    return multiply(sNum, factorial(num - 1));

}

std::string removePrecedingZeros(std::string sNum) {

    while (charToInt(sNum[0]) == 0) {
        sNum = sNum.substr(1, sNum.size());
    }
    return sNum;
}

int main(int argc, char** argv) {

    std::string fact;
    std::string sum = "0";
    for (unsigned int i = 1; i < 16; i++) {
        fact = factorial(i);
        sum = add(sum, fact);
        sum = removePrecedingZeros(sum);
    }

    std::cout << sum << std::endl;
    return 0;
}