code: void findMinElementIndexInRows(int leftmost[] )
      {
          Arrays.fill(leftmost,0,m,-1);
  
          // leftmost[i] = min(find(A(i,:)))
          for (int k = n-1; k >= 0; k--) {
              int idx0 = A.col_idx[k];
              int idx1 = A.col_idx[k+1];
  
              for( int p = idx0; p < idx1; p++ ) {
                  leftmost[A.nz_rows[p]] = k;
              }
          }
      }
docs: Computes leftmost[i] =  min(find(A[i,:))
  *
  @param leftmost (output) storage for left most elements