*********** Q2 ******************************************************
function M = transposeNegative(M)

% A pair across the main diagonal have indices (i,j) and (j,i).
% This solution moves thorough all rows and columns BELOW THE MAIN 
% DIAGONAL, at each position check the cell in the transposed 
% position and swap if both cells are negative. 
% Grading note: no new matrix

for row = 2:length(M)
     for col=1:row-1
         if (M(row,col)<0 & M(col,row)<0)  %entries (i,j)&(j,i) <0
             tmp = M(row,col);
             M(row,col) = M(col,row);
             M(col,row) = tmp;
         end
     end
end


*********** Q3 ******************************************************
% Prompt the user input
nsteps = input('Enter number of steps: ');

% generate starting coordinates : integer between -10 and 10
star_coord = floor(21*rand(1,2))-10;

x = star_coord(1);
y = star_coord(2);

for i=1:nsteps
     step_rand = floor(rand*4) % random integer number between 0-3
     if (step_rand == 0) % +1 in x direction
         x = x+1;
     elseif (step_rand == 1) % -1 in x direction
         x = x-1;
     elseif (step_rand == 2) % +1 in y direction
         y = y+1;
     elseif (step_rand == 3) % -1 in y direction
         y = y-1;
     end
     fprintf('Location after step %d: x=%d, y=%d\n',i,x,y);
end


*********** Q4 ******************************************************

int n = Keyboard.readInt();  // size of square
int col, row = 1;            // column,row number
while ( row <= n ) {
   col = 1;
   while ( col <= n ) {
      if ( row==1 || row==n || col==1 || col==n || row==col )
         System.out.print("*");
      else
         System.out.print(" ");
      col++;
   }
   System.out.println();
   row++;
}



*********** Q5 ******************************************************

public class Seesaw {
    public static void main(String[] args) {

        final int MAXCYCLES = 25;
        Person p1 = new Person();
        Person p2 = new Person();
        int cycles = 0;            // no. of cycles so far

        while ( !p1.wannaStop() && !p2.wannaStop() &&
                cycles<MAXCYCLES) {
            p1.addCalories();
            p2.addCalories();
            cycles++;
        }

        System.out.println(p1.getCalories() + p2.getCalories());
    }
} //class Seesaw

class Person {
    private int calories;
    private int calsPerCycle=10;

    public boolean wannaStop() {
        return ( Math.random() < 0.10 );
    }

    public void addCalories() {
        calories += calsPerCycle;
    }

    public int getCalories() {
        return calories;
    }
} //class Person