matrizes.java

class Main {
  
  public static void imprimeMatriz(int [][] A) {
    for(int i=0; i<A.length; i++) {
      for(int j=0; j<A[0].length; j++) {
        System.out.print(A[i][j]+" ");
      }
      System.out.println();
    }
  }
  
  public static int [][] somaMatrizes(int [][] A, int [][] B) {
    int [][] C = new int [A.length][A[0].length];
    if (A.length != B.length || A[0].length != B[0].length) return C;
    
    for(int i=0; i<A.length; i++) {
      for(int j=0; j<A[0].length; j++) {
        C[i][j] = A[i][j] + B[i][j];
      }
    }
    return C;
  }
  
  public static int [][] transposta(int [][] A) {
    int m = A.length;
    int n = A[0].length;
    int [][] At = new int [n][m];
    
    for (int i=0;i<n;i++) {
      for (int j=0; j<m; j++) {
        At[i][j] = A[j][i];
      }
    }
    return At;
  }
  
  public static boolean iguais(int [][] A, int [][] B) {
    if (A.length!=B.length || A[0].length!=B[0].length) return false;
    for (int i=0; i<A.length; i++) {
      for (int j=0; j<A[0].length; j++) {
        if(A[i][j] != B[i][j]) {
          return false;
        }
      }
    }
    return true;
  }
  
  public static int somaDiag(int [][] A) {
    if (A.length != A[0].length) return 0;
    
    int soma = 0;
    for (int i=0;i<A.length; i++) {
      soma += A[i][i];
    }
    return soma;
  }
  
  public static boolean simetrica(int [][] A) {
    if (A.length != A[0].length) return false;
    
    for (int i=0;i<A.length; i++) {
      for (int j=0; j<A[0].length; j++) {
        if (A[i][j] != A[j][i]) return false;
      }
    }
    return true;
  }
  
  public static boolean identidade(int [][] A) {
    if (A.length != A[0].length) return false;
    
    for (int i=0; i<A.length; i++) {
      for (int j=0; j<A[0].length; j++) {
        if (i==j && A[i][j]!=1) return false;
        if (i!=j && A[i][j]!=0) return false;
      }
    }
    return true;
  }
  
  public static int somaDiagSec(int [][] A) {
    if (A.length != A[0].length) return 0;
    
    int soma = 0;
    for (int i=0;i<A.length; i++) {
      soma += A[i][A.length-1-i];
    }
    return soma;
  }
  
  public static int somaLinha(int [][] A, int i) {
    int soma = 0;
    for (int j=0;j<A[0].length; j++) {
      soma += A[i][j];
    }
    return soma;
  }
  
   public static int somaColuna(int [][] A, int j) {
    int soma = 0;
    for (int i=0;i<A.length; i++) {
      soma += A[i][j];
    }
    return soma;
  }
  
  public static int [][] trocaDiags(int [][] A) {
    if (A.length != A[0].length) return A;
    
    for (int i=0;i<A.length; i++) {
      int temp = A[i][i];
      A[i][i] = A[i][A.length-1-i];
      A[i][A.length-1-i] = temp;
    }
    return A;
  }
  
  public static int [][] multMatriz(int [][] A, int [][] B) {
    int m = A.length;
    int n = B[0].length;
    int k = A[0].length;
    int [][] C = new int [m][n];
    
    if (k != B.length) return C; // não dá para multiplicar
    
    for (int i = 0; i<m; i++) {
      for (int j = 0; j<n; j++) {
        C[i][j] = 0;
        for (int l = 0; l<k; l++) {
          C[i][j] += A[i][l]*B[l][j];
        }
      }
    }
    return C;
  }
  
  public static boolean valido(int [][] A, int i, int j) {
    int m = A.length;
    int n = A[0].length;
    
    if ((i >= 0) && (i < m) && (j >= 0) && (j < n)) return true;
    return false;
  }
  
  public static int somaVizinhos(int [][] A, int i, int j) {
    int soma = 0;
    for (int k=-1; k<=1; k++) {
      for (int l=-1; l<=1; l++) {
        if ( !(k==0 && l==0) && valido(A, i+k, j+l) ){
          soma += A[i+k][j+l];
        }
      }
    }
    return soma;
  }
  
  public static void main(String[] args) {
    int [][] A = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    int [][] S = {{1, 2, 3}, {2, 5, 6}, {3, 6, 9}};
    int [][] I = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}};
    
    imprimeMatriz(A);
    System.out.println();
    imprimeMatriz(somaMatrizes(A,A));
    System.out.println();
    imprimeMatriz(transposta(A));
    System.out.println();
    System.out.println(iguais(A,A));
    System.out.println(somaDiag(A));
    System.out.println(simetrica(A));
    System.out.println(simetrica(S));
    System.out.println(identidade(A));
    System.out.println(identidade(I));
    System.out.println(somaDiagSec(A));
    System.out.println(somaLinha(A, 1));
    System.out.println(somaColuna(A, 2));
    imprimeMatriz(trocaDiags(A));
    System.out.println();
    imprimeMatriz(multMatriz(A, S));
    imprimeMatriz(A); // reparem que a matriz A foi alterada
    System.out.println(somaVizinhos(A, 2, 2));
    
  }
}