1	CS 211: Introduction to Computer Programming II Instructor: Brian M. Dennis Teaching Assistants: Tom Lechner, Bin Lin http://www.cs.northwestern.edu/~bmd/cs211/
2	Pointers int* swap(int* x_ptr, int y_ptr) { int z_ptr, z; int old_x = x_ptr; x_ptr = y_ptr; *y_ptr = old_x; return y_ptr; } int main() { int x = 10, y = 20; swap(&x, &y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
3	Arrays: access #include <iostream> using namespace std; int fib(int n); int main() { int fib_vals[10]; for(int i = 0; i < 10; i++) { fib_vals[i] = fib(i); } int j = 10; while(j--) { cout << "Fib: " << j << " = " << fib_vals[j] << "\n"; } }
4	Pointer Initialization #include <iostream> using namespace std; int main() { int* int_ptr = 0; int_ptr = NULL; char c_ptr = NULL; c_ptr = 0; char c = 'A'; char c_ptr2 = &c; c_ptr = c_ptr2; // Do some work return 0; }
5	Static Cast #include <iostream> using namespace std; int main() { int* int_ptr = 0; int_ptr = NULL; char c_ptr = NULL; c_ptr = 0; char c = 'A', c_ptr2 = &c; int_ptr = c_ptr; // Shouldn't compile return 0; }
6	C style Cast #include <iostream> using namespace std; int main() { int* int_ptr = 0; int_ptr = NULL; char c_ptr = NULL; c_ptr = 0; char c = 'A', c_ptr2 = &c; int_ptr = (int*)c_ptr; // Should compile return 0; }
7	Static Cast #include <iostream> using namespace std; int main() { int* int_ptr = 0; int_ptr = NULL; char c_ptr = NULL; c_ptr = 0; char c = 'A', c_ptr2 = &c; int_ptr = static_cast<int*>(c_ptr); return 0; }
8	Void* #include <iostream> using namespace std; int main() { int* int_ptr = 0; int_ptr = NULL; char c_ptr = NULL; c_ptr = 0; char c = 'A', c_ptr2 = &c; void* vptr = c_ptr2; int_ptr = (int)static_cast<void>(c_ptr); return 0; }
9	Array Sizing // Array sizes have to be constant expressions #include <iostream> using namespace std; int main() { int cnt = 100; int a[100], b[cnt]; cin >> cnt; int b[cnt]; // Do some other stuff }
10	Array Initialization // Arrays can be initialized #include <iostream> using namespace std; int main() { char *strings[] = { "one", "two", "three"}; for (int i = 0; i < 3; i++) { cout << strings[i] << endl; } int ints[] = { 1, 2, 3, 5, 8 }; return 0; }
11	Arrays of pointers & Pointers to pointers // Arrays can be initialized #include <iostream> using namespace std; int main() { char strings[] = { "one", "two", "three"}; strings[1] = "Hello, world"; for (int i = 0; i < 3; i++) { cout << strings[i] << endl; } char s_ptr = strings; char *s_ptr = &strings[0]; }
12	The True Main // main actually gets command line arguments #include <iostream> using namespace std; int main(int argc, char* argv[]) { for (int i = 0; i < argc; i++) { cout << argv[i] << endl; } return 0; }
13	The True Main // main actually gets command line arguments #include <iostream> using namespace std; int main(int argc, char* argv[]) { char *t_ptr = argv; while (t_ptr < argv + argc) { for (int i = 0; (t_ptr)[i]; i++) { cout << (*t_ptr)[i]; } cout << endl; t_ptr++; } return 0; }
14	The True Main // main actually gets command line arguments #include <iostream> using namespace std; int main(int argc, char* argv[]) { char *t_ptr = argv; while (t_ptr < argv + argc) { char c, t_string = t_ptr; while (c = t_string) { cout << c; t_string++; } cout << endl; t_ptr++; } return 0; }
15	const declaration // nonconstant ptr to nonconstant data #include <cctype> void convertToUppercase(char sPtr) { while (sPtr != '\0') { if (islower( sPtr )) { sPtr = toupper( *sPtr ); } ++sPtr; } }
16	const declaration // nonconstant ptr to constant data void printCharacters(const char* sPtr) { for ( ; sPtr != '\0'; sPtr++) { cout << sPtr; *sPtr = 'A'; } }
17	const declaration // constant ptr to nonconstant data int main() { int x, y; int * const ptr = &x; *ptr = 7; ptr = &x; return 0; }
18	const declaration // constant ptr to constant data int main() { int x = 5, y; const int const ptr = &x; ptr = 7; ptr = &y; return 0; }
19	Linear Search #include <iostream> using namespace std; int linearSearch(const int a[], int k, 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: "; int element = linearSearch(a, key, arraySize); if (element != -1) { cout << Found value in element: " << element << endl; } else { cout << "Value not found" << endl; } return 0; }
20	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; }
21	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: "; 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; }
22	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; }
23	That’s a Wrap Takeaways Array initialization Pointer initialization Const Pointer arithmetic Array / pointer duality Reading 4.5 – 4.9 5.5 – 5.10 2.11 – 2.12 3.10, 3.17