Unable to get desired output for the problem - c++

Question

I am trying to solve a problem here. I have two arrays which needs to be added and produce a desired output. {'A','A','A','B','A','X','M'} and {'A', 'B', 'A', 'A', 'B', 'A', 'B', 'B'}. Value of A is 10 and B is 20.
If A or B are repeated consecutively then the bonus numbers are added which is 10. I need to get an output of total score of 90 for first and 140 for second. How Can I write the perfect code.
My Code here is as below: The output should be 90 for the first array and 140 for a second. X and M have 0 value. SO don't mind them.
Here First character in array is A so score is 10
Second is also A so now 10 for A and as the previous was A so 10+10 = 20
Now as third one is also A add another 10 to previous score as 10 + 20(as last two were two as well ) ie. 30
Now fourth element in array is B so its not A and Streak is Broken so add Score For B which is set as 20
For Fifth Element we have A but as previous was Blue so no streak bonus and score of A was reset so add 10 now
Add 0 for X and M element
hence total score is 10+20+30+20+10 = 90
#include <iostream>
int main()
{
int currentEScore = 0;
int TotalScore = 0;
char Box[] = { 'A', 'A', 'A', 'B', 'A', 'X', 'M' };
// A B A R A R A A
for (int i = 0; i < Box[i]; i++) {
if (Box[i] == 'A') {
currentEScore = 10;
if (Box[i - 1] == Box[i]) {
currentEScore += 10;
TotalScore = TotalScore + currentEScore;
}
else {
TotalScore = TotalScore + currentEScore;
}
}
else if (Box[i] == 'B') {
currentEScore = 20;
if (Box[i - 1] == Box[i]) {
currentEScore += 10;
TotalScore = TotalScore + currentEScore;
}
else {
TotalScore = TotalScore + currentEScore;
}
}
else {
currentEScore = 0;
}
}
std::cout << TotalScore;
}

Answer 1

First things first: You are accessing the array out-of-bounds in the first iteration (if (Box[i - 1] == Box[i])). That is undefined behavior and strictly speaking all your code is meaningless, because a compiler is not mandated to do anything meaningful with invalid code. It just happens that this does not affect the outcome of your code. This is the worst incarnation of undefined behavior: It appears to work. You need to fix that.
Next, your loop reads for (int i = 0; i < Box[i]; i++) { and the condition cannot be correct. Again this makes your loop access the array out-of-bounds. I am a bit puzzled how this worked (I didnt realize it myself first). This also has to be fixed! I suggest to use a std::string for character arrays. It is much less error prone and it has a size() method to get its size.
The above issues didn't affect the output (nevertheless they have to be fixed!), so now lets look at the logic of your code. But first a disclaimer: Really the best advice I can give you is to not continue reading this answer. The problem you are facing is a good opportunity to learn how to use a debugger. That is a skill you will need always. If you still decide to read the following, then at least you should try to forget everything this answers says and go trough the same process on your own, by either using a debugger or a piece of paper and a pen.
Lets go step by step in your first example { 'A', 'A', 'A', 'B', 'A', 'X', 'M' }
first character is A
if (Box[i] == 'A') -> condition is true
currentEScore = 10; -> currentEScoe == 10
(we ignore the out-of-bounds for a moment)
TotalScore = TotalScore + currentEScore; -> TotalScore == 10
next character is A
if (Box[i] == 'A') -> condition is true
currentEScore = 10; -> currentEScore == 10
if (Box[i - 1] == Box[i]) -> yes
currentEScore += 10; -> currentEScore == 20
TotalScore = TotalScore + currentEScore; -> TotalScore == 10+20 == 30
next character is A
if (Box[i] == 'A') -> condition is true
currentEScore = 10; -> currentEScore == 10 -> stop... this is wrong !
You are resetting the bonus score on each character and then only check for the previous one. The effect is that you never give bonus more than 20.
Solution: Fix the out-of-bounds access and only reset the bonus when the character is different from the last. Also the code can be simplified a bit, by realizing that the bonus is indepenent from whether the character is A or B. You only have to check if it is the same as the last, hence calculating the bonus and adding points for A and B can be done seperately:
#include <iostream>
#include <string>
int main()
{
int bonus_increment = 10;
int bonus = 0;
int score_A = 10;
int score_B = 20;
int TotalScore = 0;
std::string Box{"AAABAXM"};
for (size_t i = 0; i < Box.size(); i++) {
// determine bonus
if ( i > 0 && Box[i] == Box[i-1] ) {
bonus += bonus_increment;
} else {
bonus = 0;
}
// accumulate score
if (Box[i] == 'A') {
TotalScore += score_A + bonus;
} else if (Box[i] == 'B') {
TotalScore += score_B + bonus;
}
}
std::cout << TotalScore;
}
Don't forget what I said above. You waste this exercise if you simply copy this code and assume that you completed the exercise by doing so.

Answer 2

Here's I have made some changes with your code with minimal optimization.
It'll work for you. Please check it and let me know it's working or not.
#include <iostream>
int main()
{
int currentEScore = 0;
int TotalScore = 0;
char Box[] = {'A','A','A','B','A','X','M'};
// A B A R A R A A
for (int i = 0; i < Box[i]; i++) {
if (Box[i] == 'A') {
if (Box[i - 1] == Box[i]) {
currentEScore += 10;
}
else {
currentEScore = 10;
}
}
else if (Box[i] == 'B') {
if (Box[i - 1] == Box[i]) {
currentEScore += 10;
}
else {
currentEScore = 20;
}
}
else {
currentEScore = 0;
}
TotalScore = TotalScore + currentEScore;
}
std::cout << TotalScore;
}