如何使这个代码更有效

我运行这段代码并输入值" p "， "Q"answers"101"，它似乎开始挂起。我想知道你们中的一些人使用什么样的编码和思维来帮助优化代码，使其尽可能快地运行，以及你们会对我的代码进行哪些更改。我认为主要问题在于"toSequencePos"子例程，因为它需要太长时间才能执行。

提前感谢。

[编辑]此代码是对BIO 2011的回答，可以在这里找到(问题1 A)

#include <iostream>
using namespace std;
int toNumber(char letter1)
{
    long long int position;
    switch (letter1)
    {
        case 'A': position = 1; break;
        case 'B': position = 2; break;
        case 'C': position = 3; break;
        case 'D': position = 4; break;
        case 'E': position = 5; break;
        case 'F': position = 6; break;
        case 'G': position = 7; break;
        case 'H': position = 8; break;
        case 'I': position = 9; break;
        case 'J': position = 10; break;
        case 'K': position = 11; break;
        case 'L': position = 12; break;
        case 'M': position = 13; break;
        case 'N': position = 14; break;
        case 'O': position = 15; break;
        case 'P': position = 16; break;
        case 'Q': position = 17; break;
        case 'R': position = 18; break;
        case 'S': position = 19; break;
        case 'T': position = 20; break;
        case 'U': position = 21; break;
        case 'V': position = 22; break;
        case 'W': position = 23; break;
        case 'X': position = 24; break;
        case 'Y': position = 25; break;
        case 'Z': position = 26; break;
        default:  position = 0; break;
    }
    return position;
}
int toLetter(long long int finalPosition)
{
    char letter;
    switch (finalPosition)
    {
        case 1: letter = 'A'; break;
        case 2: letter = 'B'; break;
        case 3: letter = 'C'; break;
        case 4: letter = 'D'; break;
        case 5: letter = 'E'; break;
        case 6: letter = 'F'; break;
        case 7: letter = 'G'; break;
        case 8: letter = 'H'; break;
        case 9: letter = 'I'; break;
        case 10: letter = 'J'; break;
        case 11: letter = 'K'; break;
        case 12: letter = 'L'; break;
        case 13: letter = 'M'; break;
        case 14: letter = 'N'; break;
        case 15: letter = 'O'; break;
        case 16: letter = 'P'; break;
        case 17: letter = 'Q'; break;
        case 18: letter = 'R'; break;
        case 19: letter = 'S'; break;
        case 20: letter = 'T'; break;
        case 21: letter = 'U'; break;
        case 22: letter = 'V'; break;
        case 23: letter = 'W'; break;
        case 24: letter = 'X'; break;
        case 25: letter = 'Y'; break;
        case 26: letter = 'Z'; break;
    }
    return letter;
}
int toSequencePos(long long int n1, long long int letterPos1, long long int letterPos2)
{
    long long int finalPosition = 0;
    for(long long int x = 1; x <= n1 - 2; x++)
    {
        finalPosition = letterPos1 + letterPos2;
        letterPos1 = letterPos2;
        letterPos2 = finalPosition;
    }
    while (finalPosition > 26)
    {
        finalPosition = finalPosition - 26;
    }
    return finalPosition;
}
int main()
{
    char letter1;
    char letter2;
    long long int letterPos1 = 0;
    long long int letterPos2 = 0;
    long long int sequenceLetterPos = 0;
    long long int n1;
    char finalAnswer;
    cout << "Please enter your first letter: ";
    cin >> letter1;
    letterPos1 = toNumber(letter1);
    cout << "Please enter your second letter: ";
    cin >> letter2;
    letterPos2 = toNumber(letter2);
    cout << "Please enter the position number that you wish to find in this sequence";
    cin >> n1;
    sequenceLetterPos = toSequencePos(n1, letterPos1, letterPos2);
    finalAnswer = toLetter(sequenceLetterPos);
    cout << "The letter in position " << n1 << " is " << finalAnswer << endl;
}