USACO Broze Bovine Genomics Question

Problems and Contests
#1

Hi everyone,
I just finished the problem after some debugging. The only thing I changed was how I declared varibles in my boolean function.
Before I declared them with this (setting to zero?):

int A, C, G, T;

After realizing it was the problem, I changed the declaration to this:

int A = 0; C=0, G=0, T=0;

Then the code worked. What is the difference between the two? Here is my full code:

#include<iostream>
#include<fstream>
using namespace std;
int N, M;
char spot[100][100];
char plain[100][100];
//bool function for checking a collumn of genomes
bool checkline(int collumn){
  int A = 0,C = 0,G = 0,T = 0; //variable declarations
  int A2 = -1, C2 = -1, G2 = -1, T2 = -1;
  for(int n=0; n < N; n++) { //Using ints to note whether two Genomes were used in both
    //If statements checking to see if a genome was in the seletced spot
    if(A==0 && spot[n][collumn] == 'A') {
      A = 1;
    }else if (C==0 && spot[n][collumn] == 'C') {
      C = 1;    
    }else if (G==0 && spot[n][collumn] == 'G') {
      G = 1;
    }else if (T==0 && spot[n][collumn] == 'T') {
      T = 1;
    }
    if(A2==-1 && plain[n][collumn] == 'A') {
      A2 = 1;
    }else if (C2==-1 && plain[n][collumn] == 'C') {
      C2 = 1;    
    }else if (G2==-1 && plain[n][collumn] == 'G') {
      G2 = 1;
    }else if (T2==-1 && plain[n][collumn] == 'T') {
      T2 = 1;
    }
  }
//return true or false after int setting is done
  if(A == A2 || C == C2|| G == G2||T == T2){
    return false;
  } else {
    return true;
  }
}

int main() {
  ifstream fin("cownomics.in");
  ofstream fout("cownomics.out");
  fin >> N >> M;
  for(int n = 0; n < N; n++){
    for(int m = 0; m < M; m++){
      fin >> spot[n][m];
    }
  }
  for(int n = 0; n < N; n++){
    for(int m = 0; m < M; m++){
      fin >> plain[n][m];
    }
  }
  int ans=0;
  for(int collumn = 0; collumn < M; collumn++){
    if(checkline(collumn)){
      ans++;
    }
  }
  fout << ans << "\n";
}