使用char向量的10的补数函数

Question

If you already know tens complement you can skip this whole paragraph explaining what it is.

Hello! So if you do not know to find 10's complement of a decimal number you are suppose to do 9's complement then add 1 to that number. To do 9's complement you are suppose to subtract 9 to each number, so for example your decimal number is 20. You subtract 9 to both 2 and 0 which make up 20 then you get 7 and 9. Finally you'll end up with 79 and that is the 9's complement and add 1, so 10's complement of 20 is 080. The zero in front signifies that + number. Lets say the number is a negative, -20, you need to multiply by -1 and do the same but this time we are to add a 9 in front so the number would be 980.

   vector<char> tensComplement(){

    for(std::vector<char>:: iterator i = storage.begin(); i != storage.end(); i++){
        storage[*i] = 9 - storage[*i];
    }
    storage.end() += 1;

    for(std::vector<char>:: iterator it = storage.end(); it != storage.begin(); it--){ // error for this entire loop
        if(storage[*it] == 10){
            storage[*it] = 0;
            storage[*it - 1] += 1;
        }
    }

    return storage;

}

Sorry if this is a bad question I'm still fairly new to C++. My problem is that whatever number I input I'm receiving the wrong answer. (It only works when I comment out the 2nd for loop .) The first for loop is trying to iterate through the whole vector<char> storage and subtracting it by 9. Also, for the 2nd for loop I'm receiving an error Thread 1: EXC_BAD_ACCESS (code=1, address=0x103400000) and what it is suppose to do is when the last number ends up being 10 it will carry over the one.

BigInt(int x){
    char digit;
    while (x > 0){
        digit = x % 10;
        storage.push_back(digit);
        x /= 10;
    }
    if (x < 0){
        x *= -1;
        tensComplement();
        storage.push_back(9);

    }
    else{
        tensComplement();
        storage.push_back(0);
    }

    reverse(storage.begin(),storage.end());

This is my constructor for the number, first it stores each number into my vector<char> storage and check if it is either negative or positive and do tens complement.

I just need some advice on how to fix my function and see if my constructor looks correct. Thank you so much!

Answer 1

for(std::vector<char>:: iterator it = storage.end(); it != storage.begin(); it++){ // error for this entire loop
    if(storage[*it] == 10){
        storage[*it] = 0;
        storage[*it - 1] += 1;
    }
}

The code iterating from storage.end() to storage.begin() is fishy. If you're trying to go backwards in the vector, you have to it-- ! Otherwise it'll go out of bounds in the first iteration - it's starting at the end of the vector already (which is out of bounds).