CODEWITHSUNDEEP
javamatrixcomparemultiple-columns
Lucas Bastos
Lucas Bastos

Reputation: 1

check if two rows or columns of a matrix are equal

I'm trying to check if two columns of a square matrix are equal. The function is working, but I want to reduce the complexity by using two for instead of three. It's possible? I tried a lot and I couldn't.

int a=0;
      boolean equalColumns=false;
        for(int k=0;k<this.getRows()-1;k++){
            for(int i=k;i<this.getRows()-1;i++){
                for(int j=0;j<this.getColumns();j++){
                    if(this.getElement(j, k)==this.getElement(j, i+1)){
                        a++;
                    }
                }
                if(a==this.getColumns()){
                    equalColumns=true;
                }
            }
        }

Upvotes: 0

Views: 946

Answers (2)

WJS
WJS

Reputation: 40057

I would write a method to check on two columns.

  • this uses two loops to check each column against the others.
  • if any return true, the loop short circuits and displays the result.
int n = 8;
boolean result = false;
int[][] mat = new int[n][n];
outer: for (int c1 = 0; c1 < n - 1; c1++) {
    for (int c2 = c1 + 1; c2 < n; c2++) {
        if (result = equalColumns(mat, c1, c2)) {
            break outer;
        }
    }
}
if (result) {
    System.out.println("contains equal columns");
}
  • this just takes the matrix and the columns to be checked and compares them.
  • it also short circuits as soon as a mismatch is found.
public static boolean equalColumns(int[][] mat, int cola,
        int colb) {
    for (int row = 0; row < mat.length; row++) {
        if (mat[row][cola] != mat[row][colb]) {
            return false;
        }
    }
    return true;
}

Upvotes: 0

rentox98
rentox98

Reputation: 519

Maybe I didn't understand completely your question; if you have a nXn matrix called M and you want to check if col1 and col2 are equals you can do this:

for(int row = 0; row<M.lenght;row++)
    if (M[row][col1] != M[row][col2]) return false;
return true;

Upvotes: 1

Related Questions