REC06+Problems+Set+Solutions

# REC06+Problems+Set+Solutions - 14:440:127 Introduction to...

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Unformatted text preview: 14:440:127- Introduction to Computers for Engineers Problems for students to attempt in Recitation 6- Solutions 1) Write a for loop that calculates 20! (20 factorial). You may not use the factorial( ) function. total=1; for x=1:20 % or 20:-1:1 total=total*x; end disp(total) 2) Write a while loop that continually asks the user to input a number. Each time he/she enters a positive number, you should display that number to the screen. Once the enter a number that’s not positive, the loop should stop, and you should display “Loop Stopped” to the screen. x=input( 'Enter a number' ); while (x>0) disp(x) x=input( 'Enter a number' ); end disp( 'Loop stopped' ) 3) Write a for loop that calculates the sum of the prime numbers from 1 to 1000. total=0; for x=1:1000 if (isprime(x)) total=total+x; end end disp(total) % without loops: sum(primes(1000)) 4) Write a while loop that finds the smallest 8 digit prime number. Then, instead write that loop as a for loop (using the break command). n=10000000; % smallest 8 digit number while (~isprime(n)) % loop until you find a prime n=n+1; end disp(n) for n=10000000:99999999 if (isprime(n)) break end end disp(n) 5) Use the following command to create a 10x10 matrix: C = round(500*rand(10)); Write a nested for loop that finds the maximum value in that matrix. C = round(500*rand(10)) z=size(C); maxval=-inf; for r=1:z(1) % z(1) is the number of rows in C for c=1:z(2) if (C(r,c)>maxval) maxval=C(r,c); % set maxval = to current number end end end disp(maxval) % to write this without a nested loop C = round(500*rand(10)) Cvector = C(:); % turn C into a vector maxval=-inf; for e=1:length(Cvector) if (Cvector(e)>maxval) maxval=Cvector(e); end end disp(maxval) 6) Write a loop that creates the following matrix. Notice that the first row is 1*[4 8 12], the second row is 2*[4 8 12], the third row 3*[4 8 12], etc....
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REC06+Problems+Set+Solutions - 14:440:127 Introduction to...

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