A practical introduction to Pascal programming language - GIARA

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Data structuresProgram 81: Exercise 4.4 (version C)program c04e04;constN=10;typeintVector=ARRAY[1..N] OF integer;vari:integer;myVector:intVector;min,max,sum:integer;mean:real;beginwriteln(’Introduce the vector of ’,N,’ elements, splitted by blank spaces.’);(* Reading the first value *)read(myVector[1]);(* Setting the initial values *)min:=myVector[1];max:=myVector[1];sum:=myVector[1];(* Reading and processing the remaining values *)for i:=2 to N dobeginread(myVector[i]);if (myVector[i]max) thenmax:=myVector[i];sum:=sum+myVector[i]end;mean:=sum/N;writeln(’The max is ’,max,’, the min is ’,min,’, and the mean is ’,mean:3:3,’.’)end.⊡Exercise 4.5. Create a program that reads a vector of N integers (being N a constant), then findsout its standard deviation.□The difference between this exercise and the previous is the fact that we need at least twoiterations over the values of the array to compute the expected result. The reason is that, inorder to compute the standard deviation, we need to know the mean of the values. Hence, afirst pass through the vector has to be accomplish to compute the mean, followed by a secondone to compute the standard deviation.Program 82: Exercise 4.5program c04e05;constN=5;typeintVector=ARRAY[1..N] OF integer;vari:integer;myVector:intVector;mean,std:real;begin(* Reading *)71
A Practical Introduction to Pascal Programming Language⊡writeln(’Introduce the vector of ’,N,’ elements, splitted by blank spaces.’);(* First pass computing the mean *)mean:=0;for i:=1 to N dobeginread(myVector[i]);mean:=mean+(myVector[i]/N)end;(* Second pass computing the standard deviation *)std:=0;for i:=1 to N dostd:=std+( (sqr(myVector[i]-mean))/N);std:=sqrt(std);writeln(’The mean is ’,mean:3:3,’ and the standard deviation is ’,std:3:3,’.’)end.Exercise 4.6. Create a program that reads a vector A of N reals (being N a constant), and creates anew vector so that at every position i it contains the sum of all the values of A up to that position.□Initially, this problem is solved by using a double loop. First, we have to read the vector A.Then, for each position i, we perform an iteration up to that position accumulating the valuesstored in the vector A. Note that it is necessary a good practice to initialize the values in thevector B to 0.Program 83: Exercise 4.6 (Version A)program c04e06;constN=5;typeintVector=ARRAY[1..N] OF integer;vari,j:integer;A,B:intVector;begin(* Reading *)writeln(’Introduce the vector of ’,N,’ elements, splitted by blank spaces.’);for i:=1 to N dobeginread(A[i]);end;(* Accumulating *)for i:=1 to N dobeginB[i]:=0;for j:=1 to i doB[i]:=B[i]+A[j]end;(* Accumulating *)write(’The values in the vector are: ’);for i:=1 to N dowrite(B[i],’ ’);end.The exercise in the past form is not very efficient. Every time we increase the value of i, werecalculate the sum of all the values up to i-1. However, that sum is already stored in B[i].Hence, the solution can be simplified (and enhanced) by making use of such values72
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A Practical Introduction to Pascal
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ContentsIntroduction to this book 9
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