Functions Dr. Sajib Datta CSE@UTA

Multiple value return In your function, the key word “return” can only return a single value, NOT multiple values. But you can define an array in main function body, and pass it to your function. In your function, we may store multiple values in that array, which will be visible in the main function. So it is sort of returning multiple values. See the example in the next slide.

A function to return the min and the max of an array of integers #include <stdio.h> void minmax(int myarr[], int myminmax [], int s); int main(void) { int arr[] ={42, 2, 443, 23, 12}, minmaxarr[2], size; size = sizeof(arr)/sizeof(int); minmax(arr, minmaxarr, size); printf("The array has a minimum value of %d, and a maximum value of %d.\n", minmaxarr[0], minmaxarr[1]); return 0; } void minmax(int myarr[], int myminmax [], int s) int i; myminmax[0] = myarr[0];// myminmax[0] for the minimum value myminmax[1] = myarr[0];// myminmax[1] for the maximum value for(i = 1; i < s; i ++) if (myminmax[0] > myarr[i]) myminmax[0] = myarr[i]; else if (myminmax[1] < myarr[i]) myminmax[1] = myarr[i];

Recursion Recursive Function Definition Why Recursive Function Recursive function is a function that contains a call to itself. Why Recursive Function Recursive function allows you to divide your complex problem into identical single simple cases which can handle easily. Note on Using Recursive Function Recursive function must have at least one exit condition that can be satisfied. Otherwise, the recursive function will call itself repeatedly into a dead loop until the runtime stack overflows.

Recursion # include<stdio.h> int sum(int number) { if(number <= 1) return 1; return number + sum(number - 1); } void main() int x = 5; printf("The sum of all positive integers (<= %d) is %d.\n", x, sum(x)); return 0; How to implement factorial?

Fibonacci Sequence Define a recursive function to implement FS Given n, print out the first n integers in FS 0,1,1,2,3,5,8,13,21,34,55…..(1st 10 numbers)

#include <stdio.h> int fibonacci(int n); int main(void) { int input, i; printf("Please input a positive integer value:"); scanf("%d", &input); for(i = 0; i <= input; i++) printf("%d ", fibonacci(i)); } int fibonacci(int n) if(n < 2) return n; else return fibonacci(n-1)+fibonacci(n-2);

Binary Search

while(left <= right) { mid = (left+right)/2; if(intarr[mid] == target) printf("The index of the target in the array is %d.\n", mid); break; } else if (target > intarr[mid]) left = mid + 1; else right = mid - 1; if(left > right) printf("The target is not in the array.\n"); return 0; #include <stdio.h> #define ARRSIZE 7 int main(void) { int intarr[ARRSIZE], target, i, left, right, mid; printf("Please input %d integers which are sorted in the ascending order and a target value.", ARRSIZE); scanf("%d", &target); for(i = 0; i<ARRSIZE; i++) scanf("%d", &intarr[i]); } left = 0; right = ARRSIZE-1;

Binary Search- Recursive #include<stdio.h> #define ARR_SIZE 10 void binarySearch(int arr[], int left, int right, int t); int main(void) { int intarr[ARR_SIZE] = {-12, -3, 0, 5, 11, 15, 27, 33, 49, 59}, target; puts("Please input a target value:"); scanf("%d", &target); binarySearch(intarr, 0, ARR_SIZE-1, target); return 0; } void binarySearch(int arr[], int left, int right, int t) { int mid; printf("The current range is %d, %d.\n", left, right); if(left<=right) mid = (left+right)/2; if(arr[mid] == t) printf("The index of the target is %d.\n.", mid); else if(arr[mid] > t) binarySearch(arr, left, mid-1, t); else binarySearch(arr, mid+1, right, t); } printf("The target is not found.");