Chapter 7 Solved problems

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1 Chapter 7 7.4, Section D 20. The coefficients of a polynomial function are stored in a single-dimensional array. Display its derivative. If the polynomial function is p(x) = a n x n + a n-1 x n a 3 x 3 + a 2 x 2 + a 1 x + a 0 its derivative is p (x)= na n x n-1 + (n-1)a n-1 x n a 3 x 2 + 2a 2 x + a 1 Program int v[20], d[20], n, i; printf("v[%d]=",i); scanf("%d", &v[i]); printf("function:\n"); printf(" %+dx^%d",v[i],n-1-i); printf("\n"); for(i=0;i<n-1;i++) d[i]=v[i]*(n-1-i); printf("derivative:\n"); for(i=0;i<n-1;i++) printf(" %+dx^%d",d[i],n-2-i);

2 Computer Programming The C Language 24. Verify if a square matrix is the identity (or the unit) matrix (if it contains 1s on the main diagonal and 0s elsewhere). The matrix is initially considered the identity matrix and if an element that doesn t satisfy the criteria is found, than the check ends because the matrix is not the identity matrix. Program int a[20][20], n, i, j, flag=1; for(j=0;j<n;j++){ printf("a[%d][%d]=", i,j); scanf("%d", &a[i][j]); for(j=0;j<n;j++) printf("%5d ", a[i][j]); printf("\n"); for(j=0;j<n;j++){ if(i==j){ /*the element belongs to the main diagonal*/ if(a[i][j]!=1){ flag=0; else /*the element doesn't belong to the main diagonal*/ if(a[i][j]!=0){ flag=0; if(flag==0) 2

3 if(flag) printf("identity matrix"); else printf("not identity"); 25. Verify if a square matrix is symmetric with respect to the main diagonal. The upper or the lower triangle of the main diagonal must be traversed and the statement a[i][j]==a[j][i] must be verified. Program int a[20][20], n, i, j, flag=1; for(j=0;j<n;j++){ printf("a[%d][%d]=", i,j); scanf("%d", &a[i][j]); for(j=0;j<n;j++) printf("%5d ", a[i][j]); printf("\n"); for(j=i+1;j<n;j++){ if(a[i][j]!=a[j][i]){ flag=0; if(flag==0) if(flag) printf("simetric"); else printf("not"); 3

Computer Programming The C Language Chapter 9 9.4, Section D 15. Two marks are read from the keyboard (the mark for the exam and the mark for the lab); they are stored in pointer variables.

4 Computer Programming The C Language Chapter 9 9.4, Section D 15. Two marks are read from the keyboard (the mark for the exam and the mark for the lab); they are stored in pointer variables. Display the final mark (the mark for the exam is 2/3 of the final mark and the mark for the lab is 1/3 of the final mark). Program int *e, *l, exam, lab; float *f, finalmark; e=&exam; l=&lab; f=&finalmark; printf("exam: "); scanf("%d", e); printf("lab: "); scanf("%d", l); *f=(float)(2*(*e)+(*l))/3; printf("the finl mark: %.2f", *f); getch(); 16. The elements of a vector with integer numbers are read from the keyboard. Traverse this vector using a pointer and display the value of its first negative element. Program int v[30], n, i, *p, flag=0; 4

5 for(p=v,i=0;p<v+n;p++,i++){ printf("v[%d]=",i); scanf("%d", p); printf("\nthe vector: "); for(p=v;p<v+n;p++) printf("%d ", *p); for(p=v;p<v+n;p++) if(*p<0){ printf("\nthe first negative element: %d", *p); flag=1; if(flag==0) printf("\nno negative elements"); getch(); 17. The first name and the last name of a student are read in two variables char *. Create a third string (also a pointer of type char) that contains the first name followed by the second name (separated through a space). Program #include <string.h> char *fn, *ln, *fulln, first_name[20], last_name[20], full_name[30]; fn=first_name; ln=last_name; fulln=full_name; printf("first name: "); gets(fn); printf("last name: "); gets(ln); strcpy(fulln,fn); strcat(fulln," "); strcat(fulln,ln); puts(fulln); getch(); 5

6 Computer Programming The C Language 18. A text t and two words w1 and w2 are read from the keyboard. Display the string that is obtained by replacing in text t all the occurrences of w1 with w2. Program #include <string.h> char t[50], w1[20], w2[20], finaltext[50]="",*p; printf("the text: "); gets(t); printf("the first word: "); gets(w1); printf("the second word: "); gets(w2); while(strstr(t,w1)!=null){ p=strstr(t,w1); //where w1 is found in t strncat(finaltext, t, p-t); strcat(finaltext,w2); strcpy(t,p+strlen(w1)); strcat(finaltext,t); puts(finaltext); Other solved problems 1. Repetitive menu. The program executes some actions on a vector of integers, according to a menu that is repetitively displayed. Program 1 #include <stdlib.h> 6

7 int marks[50],n,i,option,counter=0,sum=0,flag=0; float average; printf("marks[%d]=",i); scanf("%d", &marks[i]); while(1){ system("cls"); printf("\n1 - Display left to right"); printf("\n2 - Display right to left"); printf("\n3 Number of students who passed the exam"); printf("\n4 - The average of all marks"); printf("\n5 - Index of mark 10"); printf("\n0 - Exit"); printf("\nyour option: "); scanf("%d", &option); switch(option){ case 1: printf("%d ", marks[i]); case 2: for(i=n-1;i>=0;i--) printf("%d ", marks[i]); case 3: if(marks[i]>=5) counter++; printf("%d students passed the exam", counter); case 4: sum+=marks[i];//sum=sum+marks[i]; average=(float)sum/n; printf("the average is: %.2f", average); 7

8 Computer Programming The C Language case 5: if(marks[i]==10){ printf("%d ", i); flag=1; if(flag==0) printf("no students with mark 10"); case 0: exit(0); default: printf("wrong option!"); printf("\n"); system("pause"); //getch(); 2. Array of strings. A matrix of chars is used to store some names. Each row of the matrix is accessed as a string, not char by char. Program 2 #include <string.h> char students[20][20], name[20]; int n, i, flag=0; printf("how many students? "); scanf("%d", &n); fflush(stdin); printf("student %d: ", i); gets(students[i]); system("cls"); printf("the sudents are:\n"); printf("%s\n", students[i]); 8

$printf("\n\nthe name of the student you are looking for: "); gets(name);$

9 printf("\n\nthe name of the student you are looking for: "); gets(name); if(strcmp(students[i],name)==0){ printf("\nfound %s\n", name); flag=1; if(flag==0) printf("\nnot found"); getch(); 9

Chapter 01 Arrays Prepared By: Dr. Murad Magableh 2013

Chapter 01 Arrays Prepared By: Dr. Murad Magableh 2013 One Dimensional Q1: Write a program that declares two arrays of integers and fills them from the user. Then exchanges their values and display the