one dimentional array on programming with C

One-Dimensional Arrays (1DA) ECE1101: Programming Fundamentals

 1DA Definition  1DA Declaration  1DA Initialization  1DA Assignment  1DA Input / Output  Examples Agenda

• An array is a group of contiguous memory locations that all have the same type. • It help us to organize large amounts of information • AKA list, vector, single array, … etc. 1DA Definition

Example: The Scores Array The entire array has a single name Each value has a numeric index An array of size N is indexed from zero to N-1 This array holds 9 values that are indexed from 0 to8

 A particular value in an array is referenced using the array name followed by the index in brackets  For example, the expression scores[2] refers to the value 12 (the 3rd value in the array)  That expression represents a place to store a single integer and can be used wherever an integer variable can be used 1DA Definition

 For example, an array element can be assigned a value, printed, or used in a calculation: int first=3 scores[2] = 89; scores[first] = scores[first] + 2; mean = (scores[0] + scores[1])/2; printf ("Top = %d”, scores[5]); 1DA Definition

 The values held in an array are called array elements  An array stores multiple values of the same type (the element type)  The element type can be a primitive type or a structure.  Therefore, we can create an array of integers, or an array of characters, etc. 1DA Definition

1DA Declaration The variable scores is set to a new blank array that can hold 9 integers

Bounds Checking  Once an array is created, it has a fixed size  An index used in an array reference must specify a valid element  That is, the index value must be in bounds (0 to N-1)  For example, if the array codes can hold 100 values, it can be indexed using only the numbers 0 to 99  If count has the value 100, then the following reference will cause a problem: for (int index=0; index <= 100; index++) codes[index] = index*50 + epsilon; problem

1DA Initializing  We can declare and initialize an array in one step  The values are delimited by braces and separated by commas  Examples: char letterGrades[ ] = {'A', 'B', 'C', 'D', ’F'};

Initializer Lists  Note that when an initializer list is used:  no size value is specified  The size of the array is determined by the number of items in the initializer list  An initializer list can only be used only in the array declaration.

Note One array cannot be copied to another using assignment.

Parallel Arrays  These are independent arrays of the same size, that have a meaningful connection to each other.  For example, one array with a students gpa, and one with his letter grade.

• We typically use for loops for any kind of array processing. • To input an array, one by one: for (i=0; i<10 ; i++ ) { printf(“ Enter element %d : “, i ); scanf ( “ %d “, &scores[i] ); } 1DA Input / Output

• To display an array, one element per line: for (i=0; i<10 ; i++ ) { printf(“ scores [%d] : %dn“, i , scores[i] ); } 1DA Output

• double X[ ]= {16.0, 12.0, 6.0, 8.0, 2.5, 12.0, 14.0, -54.5} • int i=5; • printf(“%f”, x[4]); • printf(“%f”, x[i]+1); • printf(“%f”, x[i+1]); • printf(“%f”, x[2*i]); • printf(“%f”, x[2*i-3]); • printf(“%f”, x[(int) x[4]]); • printf(“%f”, x[i++]); • printf(“%f”, x[--i]); • x[i]= x[i+1]; Sample Trace Problem  Show the output of the following C-code segment:

Sample Write Problems 1. Write a C-program that reads 5 student scores in order to compute their average: a. Don’t use loop neither array. b. Use loop but don’t use array. c. Use array but don’t use loop. d. Use array and loop 2. Write a C-program that reads a list of 5 student scores then call a function to compute their average. 3. Write a C-program that reads a list of 5 student scores then call a function to compute & display their average. 4. Write a C-program that call a function to reads a list of 5 student scores to display their average.

#include <stdio.h> int main( void ) { //declaration part float score1, score2, score3, score4, score5, sum, avg; //input step printf(“score1= ”); scanf(“%f”, &score1); printf(“score2= ”); scanf(“%f”, &score2); printf(“score3= ”); scanf(“%f”, &score3); printf(“score4= ”); scanf(“%f”, &score4); printf(“score5= ”); scanf(“%f”, &score5); //calc step sum = score1 + score2 + score3 + score4 + score5 ; avg= sum/5; //output step printf( “Average of 5 scores=%fn", avg); return 0; } Solution-1a: No loop No array We used separate variable for each score

#include <stdio.h> int main( void ) { //declaration part float score, sum, avg; //input & calc steps sum=0; for(int i=1; i<=5; i++) { printf(“score%d=”, i); scanf(“%f”, &score); sum = sum + score; } avg= sum/5; //output step printf( “Average of 5 scores= %fn", avg); return 0; } Solution-1b: loop but No array We used single variable to read all scores

#include <stdio.h> #define SIZE 5 int main( void ) { //declaration part float scoreArr[SIZE], sum, avg; //input step printf(“score1= ”); scanf(“%f”, &scoreArr[0]); printf(“score2= ”); scanf(“%f”, &scoreArr[1]); printf(“score3= ”); scanf(“%f”, &scoreArr[2]); printf(“score4= ”); scanf(“%f”, &scoreArr[3]); printf(“score5= ”); scanf(“%f”, &scoreArr[4]); //calc step sum = scoreArr[0] + scoreArr[1] + scoreArr[2] + scoreArr[3] + scoreArr[4] ; avg= sum/SIZE; //output step printf( “Average of %d scores=%fn", SIZE, avg); return 0; } Solution-1c: array but No loop We used separate variable for each score It is a good practice to define the array size as constant

#include <stdio.h> #define SIZE 5 int main( void ) { //declaration part float scoreArr[SIZE], sum, avg; //input & calc steps sum=0; for(int i=0; i<SIZE; i++) { printf(“score%d=”, i+1); scanf(“%f”, &scoreArr[i]); sum = sum + scoreArr[i]; } avg= sum/SIZE; //output step printf( “Average of %d scores= %fn", SIZE, avg); return 0; } Solution-1d: array & loop We used separate variable for each score

#include <stdio.h> #define SIZE 5 int main( void ) { //declaration part float scoreArr[SIZE], sum, avg; //input step for(int i=0; i<SIZE; i++) printf(“score%d=”, i+1); scanf(“%f”, &scoreArr[i]); //calc step sum=0; for(int i=0; i<SIZE; i++) sum = sum + scoreArr[i]; avg= sum/SIZE; //output step printf( “Average of %d scores= %fn", SIZE, avg); return 0; } Another Solution-1d: array & loop We used separate variable for each score

#include <stdio.h> #define SIZE 5 float avgFun(float arr[ ], int size); int main( void ) { //declaration part float scoreArr[SIZE], avg; //input step for(int i=0; i<SIZE; i++) printf(“score%d=”, i+1); scanf(“%f”, &scoreArr[i]); //calc step avg= avgFun(scoreArr, SIZE); //output step printf( “Average of %d scores= %fn", SIZE, avg); return 0; } float avgFun(float arr[ ], int size) { float sum=0; for(int i=0; i<size; i++) sum = sum + arr[i]; return sum/size; } Solution-2: only calc in function We used separate variable for each score Passing arrays to functions is always call by reference

#include <stdio.h> #define SIZE 5 void avgFun(float arr[ ], int size); int main( void ) { //declaration part float scoreArr[SIZE]; //input step for(int i=0; i<SIZE; i++) printf(“score%d=”, i+1); scanf(“%f”, &scoreArr[i]); //calc & output steps avgFun(scoreArr, SIZE); return 0; } void avgFun(float arr[ ], int size) { //calc step float sum=0; for(int i=0; i<size; i++) sum = sum + arr[i]; //output step printf( “Average of %d scores= %fn", size, sum/size); } Solution-3: calc & o/p in function We used separate variable for each score Passing arrays to functions is always call by reference

#include <stdio.h> #define SIZE 5 void avgFun( void ); int main( void ) { //input, calc & output steps avgFun( ); return 0; } void avgFun( void ) { //declaration part float scoreArr[SIZE]; //input step for(int i=0; i<SIZE; i++) printf(“score%d=”, i+1); scanf(“%f”, &scoreArr[i]); //calc step float sum=0; for(int i=0; i<SIZE; i++) sum = sum + scoreArr[i]; //output step printf( “Average of %d scores= %fn", SIZE, sum/SIZE); } Solution-4: i/p, calc & o/p in function We used separate variable for each score Writing void in parameter list is optional

Sample Write Problems  Write a program that reads in an array of 10 integers (range 0 - 50, strict) and then draws a bar chart of the values: 10 ********** 5 ***** 15 *************** ….

Array searching  Write a program that reads in an array of 50 numbers and then prints out their maximum.  Solve again by using function to get the maximum  Write a program that reads in the grades of 500 students in an exam and then display the success ratio.  Write a program that reads in an array of 10 student grades, adds up 2 points to each grade (making sure no one goes over 100), and then tells you how many students got an A (over 85).

Handling multiple arrays  Write a program that reads in the id and grades of 30 students. Then it prints out the id of the highest scoring student.  Write a program that reads in an array of grades for 30 students and creates another array for failed students only  Write a program that creates 3 arrays for the id, price, and quantity of items being sold in a shop. The program prints the data in a table format.The program then prints out the ids of all items whose quantity is less than 10, and those items whose price is > 100.

/* Reads data into two arrays and subtract their corresponding elements, storing the result in another array. */ #include<stdio.h> #define SIZE 5 int main(void){ int first[SIZE], second[SIZE], diff[SIZE], i; // declaration part printf("Enter %d data items for first array : ", SIZE); for(i=0;i<SIZE; i++) // input first array scanf("%d",&first[i]); printf("Enter %d data items for second array : ", SIZE); for(i=0;i<SIZE; i++) // input second array scanf("%d",&second[i]); for(i=0;i<SIZE; i++) // calculate the differences diff[i]=second[i] - first[i]; printf("nnOutput of the arrays : n"); for(i=0;i<SIZE; i++) // output the arrays printf("%5d %5d %5dn", first[i], second[i], diff[i]); system("pause"); return 0; } example

one dimentional array on programming with C

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