CS 211:
Introduction to Computer Programming II

	Instructor: Brian M. Dennis
	Teaching Assistants:
	Tom Lechner, Bin Lin
	http://www.cs.northwestern.edu/~bmd/cs211/

Linear Search

	#include <iostream>
	using namespace std;
	int linearSearch(const int a[], int k, const int size);
	int main() {
	const int arraySize = 100;
	int a[arraySize];
	int key;
	for (int i = 0; i < arraySize; i++) {
	a[i] = 2 * i;
	}
	cout << "Enter integer search key: ";
	cin >> key;
	int element = linearSearch(a, key, arraySize);
	if (element != -1) {
	cout << "Found value in element: " << element << endl;
	} else {
	cout << "Value not found" << endl;
	}
	return 0;
	}

Linear Search

	int linearSearch(const int array[], int key, int sizeOfArray) {
	for (int j = 0; j < sizeOfArray; j++) {
	if (array[j] == key) {
	return j;
	}
	}
	return -1;
	}
	int linearSearch(const int array[], int key, int sizeOfArray) {
	const int *t_array = array;
	while (t_array < (array + sizeOfArray)) {
	if (*t_array++ == key) {
	return (t_array – array – 1);
	}
	}
	return -1;
	}

Binary Search

	#include <iostream>
	using namespace std;
	int binarySearch(const int a[], int k, int low, int high, int size)
	int main() {
	const int arraySize = 100;
	int a[arraySize];
	int key;
	for (int i = 0; i < arraySize; i++) {
	a[i] = 2 * i;
	}
	cout << "Enter integer search key: ";
	cin >> key;
	int element = binarySearch(a, key, 0, arraySize – 1, arraySize);
	if (element != -1) {
	cout << "Found value in element: " << element << endl;
	} else {
	cout << "Value not found" << endl;
	}
	return 0;
	}

Binary Search

	int binarySearch(const int a[], int searchKey, int low, int high,
	int size)
	{
	int middle;
	while (low <= high) {
	middle = (low + high) / 2;
	if (searchKey == a[middle]) {
	return middle;
	} else if (searchKey < a[middle]) {
	high = middle – 1;
	} else {
	low = middle + 1;
	}
	}
	return -1;
	}

const declaration

	// nonconstant ptr to nonconstant data
	#include <cctype>
	void convertToUppercase(char *sPtr) {
	while (*sPtr != '\0') {
	if (islower( *sPtr )) {
	*sPtr = toupper( *sPtr );
	}
	++sPtr;
	}
	}

const declaration

	// nonconstant ptr to constant data
	void printCharacters((const char)* sPtr) {
	for ( ; *sPtr != '\0'; sPtr++) {
	cout << *sPtr;
	*sPtr = 'A'; // Should be an error
	}
	}

const declaration

	// constant ptr to nonconstant data
	int main() {
	int x, y;
	int * const ptr = &x;
	*ptr = 7;
	ptr = &x;
	return 0;
	}

const declaration

	// constant ptr to constant data
	int main() {
	int x = 5, y;
	const int *const ptr = &x;
	*ptr = 7;
	ptr = &y;
	return 0;
	}

String Functions

	// #include <cstring>
	char *strcpy(char *s1, const char *s2);
	char* strncpy(char* s1, const char* s2,
	size_t n);
	char* strcat(char* s1, const char *s2);
	char* strncat(char *s1, const char* s2,
	size_t n);
	int strcmp(const char* s1, const char *s2);
	int strncmp(const char* s1, const char* s2,            size_t n);
	size_t strlen(const char *s);

String length

	#include <cstring>
	#include <iostream>
	using namespace std;
	int main(int argc, char* argv[]) {
	int total_length = 0;
	for(int i = 1; i < argc; i++) {
	total_length += strlen(argv[i]);
	}
	cout << "Total characters: " << total_length
	<< endl;
	return 0;
	}

String copying

	#include <iostream>
	#include <cstring>
	using namespace std;
	int main(int argc, char *argv[]) {
	const int BUF_SIZE = 1024;
	char buf[BUF_SIZE] = { '\0' };
	for(int i = 1; i < argc; i++) {
	strcpy(buf, argv[i]);
	}
	return 0;
	}

String concatenation

	#include <iostream>
	#include <cstring>
	using namespace std;
	int main(int argc, char *argv[]) {
	const int BUF_SIZE = 1024;
	char buf[BUF_SIZE] = { '\0' };
	for(int i = 1; i < argc; i++) {
	strcat(buf, argv[i]);
	}
	cout << "Command line glommed together.\n";
	cout << buf << endl;
	return 0;
	}

Binary Search w/Strings

	#include <iostream>
	using namespace std;
	int binarySearch(char** a, char* k,
	int low, int high, int size);
	int main() {
	char* strings[] = { "Go", "Northwestern",
	"Wildkats", "You" };
	char search_key[1024];
	cout << "Enter string search key: ";
	cin >> search_key;
	int element = binarySearch(strings, search_key,
	0, 3, 3);
	if (element != -1) {
	cout << "Found value in element: " << element
	<< endl;
	} else {
	cout << "Value not found" << endl;
	}
	return 0;}

Binary Search w/Strings

	int binarySearch(char** a, char* searchKey,
	int low, int high, int size)
	{
	int middle;
	while (low <= high) {
	middle = (low + high) / 2;
	int cmp_res = strcmp(searchKey, a[middle]);
	if (!cmp_res) {
	return middle;
	} else if (cmp_res < 0) {
	high = middle - 1;
	} else {
	low = middle + 1;
	}
	}
	return -1; }

Dangling Pointers

	#include <cstdlib>
	#include <time>
	char* random_string(int n_chars) {
	srand( time(0));
	const int max_size = 80;
	char buf[max_size] = {'\0'};
	for (int i = 0;
	(i < n_chars) && (i < max_size));
	i++) {
	int offset = rand() % 26;
	buf[i] = 'a' + offset;
	}
	return buf;
	}

Dynamic Allocation

	#include <iostream>
	#include <cstring>
	using namespace std;
	int main(int argc, char* argv[]) {
	int  buf_length = 0;
	for(int i = 1; i < argc; i++) {
	buf_length += strlen(argv[i]);
	}
	buf_length++;
	char* buf = new char[buf_length];
	buf[0] = '\0';
	for (int j = 1; j < argc; j++) {
	strcat(buf, argv[i])
	}
	cout << "Command line glommed together\n";
	cout << buf << endl;
	delete buf;
	return 0;
	}

That’s a Wrap

	Reading
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