13 - ICS103 Programming in C Lecture 13 Arrays II 1 Outline Review on Arrays Using array elements as function arguments Examples Using arrays as

13 - ICS103 Programming in C Lecture 13 Arrays II 1 Outline...

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1 ICS103 Programming in C Lecture 13: Arrays II
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2 Outline Review on Arrays Using array elements as function arguments Examples Using arrays as function arguments Array as formal parameter to functions Array as actual argument in function call Examples Returning an array result Examples Partially filled Arrays Example
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3 Review: Recall the following example /* Computes the mean and standard deviation of an array of data and displays the difference between each value and the mean. */ #include <stdio.h> #include <math.h> #define SIZE 8 /* maximum number of items in list of data */ int main(void) { double x[SIZE], mean, st_dev, sum, sum_sqr; int i; /* Gets the data */ printf("Enter %d numbers separated by blanks\n> ", SIZE); for (i = 0; i < SIZE; ++i) scanf("%lf", &x[i]); /* Computes the sum and the sum of the squares of all data */ sum = 0; sum_sqr = 0; for (i = 0; i < SIZE; ++i) { sum += x[i]; sum_sqr += x[i] * x[i]; }
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4 Example 3… /* Computes and prints the mean and standard deviation */ mean = sum / SIZE; st_dev = sqrt(sum_sqr / SIZE - mean * mean); printf("The mean is %.2f.\n", mean); printf("The standard deviation is %.2f.\n", st_dev); /* Displays the difference between each item and the mean */ printf("\nTable of differences between data values and mean\n"); printf("Index Item Difference\n"); for (i = 0; i < SIZE; ++i) printf("%3d%4c%9.2f%5c%9.2f\n", i, ' ', x[i], ' ', x[i] - mean); system("pause"); return (0); }
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5 Using array elements as function arguments From the last example, we note that x[i] is used as actual arguments to both printf and scanf functions. for (i = 0; i < SIZE; ++i) scanf("%lf", &x[i] ); When i is 3 for example, &x[i] in the above stement passes the address of the 4 th array element , to the scanf function. printf("%3d%4c%9.2f%5c%9.2f\n", i, ' ', x[i], ' ', x[i] - mean); Similarly, when i=3, x[i] in the above statement passes the value of the 4 th element to the printf function. Thus, the important point to note is that array elements are treated as scalar variables and can be used wherever scalar variables can be used. For example, if we have a double array, double a[8]; a[0] = 4.5; Then we can make a function call: double root = sqrt(a[0]); This rule applies to all cases including user defined functions.
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6 Example 1 /* Finds the square roots of all elemets in an array */ #include <stdio.h> #include <math.h> #define SIZE 8 /* maximum number of items in list of data*/ int main(void) { double x[SIZE], result[SIZE]; int i; /* Gets the data */ printf("Enter %d numbers separated by blanks\n> ", SIZE); for (i = 0; i < SIZE; ++i) scanf("%lf", &x[i]); /* Computes the square roots */ for (i = 0; i < SIZE; ++i) result[i] = sqrt(x[i]); /* notice the argument pass to sqrt function */ /* print the result */ printf("\tx\tsqrt(x)\n"); for (i = 0; i < SIZE; ++i) printf("%9.2f%4c%9.2f%\n", x[i], ' ', result[i ]); system("pause"); return 0; }
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7 Example 2 /* uses a function to count even and odd numbers from an integer array */ #include <stdio.h> #define SIZE 8 /* maximum number of items in list of data*/ int is_even(int n); int main(void) { int a[SIZE]; int i, evens = 0, odds = 0; /* Gets the data */ printf("Enter %d integer numbers separated by blanks\n> ", SIZE); for (i = 0; i < SIZE; ++i) scanf("%d", &a[i]); /* counts the even and odd numbers */ for (i = 0; i < SIZE; ++i) { if (is_even(a[i])) /* notice the argument pass to is_even function */ evens++; else odds++; }
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