strstr char str Ding Dong char res strstrstr

strstr הפונקציה char str[] = “Ding Dong”; char *res = strstr(str, ”Don”); 6500 str D 6500 i n g D o n g res printf(“res=%pn”, res); printf(“res=%sn”, res); res=6505 res=Dong

דוגמא – כמה פעמים מופיעה מילה בשיר int main() { const char rhyme[] = "Humpty Dumpty sat on a wall, n " "Humpty Dumpty had a great fall. n " "All the king's horses, n" "And all the king's men, n" "Couldn't put Humpty together again. n"; const char humpty[] = "Humpty"; char *ptr = NULL; int count = 0; for (ptr = strstr(rhyme, humpty); ptr != NULL; ptr = strstr(ptr + 1, humpty)) { count++; } printf("The string %s appears %d timesn", humpty, count); return 0; }

דוגמא נחפש את . . . 56 9 8 7 6 5 4 3 2 1 0 index 97 57 56 22 11 8 4 0 -3 -5 value 13

דוגמא נחפש את . . . 4 9 8 7 6 5 4 3 2 1 0 index 97 57 56 22 11 8 4 0 -3 -5 value 14

Code – Binary Search int binary. Search. Rec(int arr[], int quary, int start, int end) { int middle; if (start > end) return -1; middle = start + (end-start) / 2; if (arr[middle] == quary) return middle; if (arr[middle] > quary) return binary. Search. Rec(arr, quary, start, middle-1); else return binary. Search. Rec(arr, quary, middle+1, end); } 15

Code – Main int a [] = {-5, -3, 0, 4, 8, 11, 22, 56, 57, 97}; printf("%dn", binary. Search(a, SIZE, 0)); printf("%dn", binary. Search(a, SIZE, -4)); printf("%dn", binary. Search(a, SIZE, 8)); printf("%dn", binary. Search(a, SIZE, 1)); printf("%dn", binary. Search(a, SIZE, -5)); printf("%dn", binary. Search(a, SIZE, 9)); printf("%dn", binary. Search(a, SIZE, 7)); int binary. Search(int arr[], int size, int quary) { return binary. Search. Rec(arr, quary, 0, size-1); } 16

Output int a [] = {-5, -3, 0, 4, 8, 11, 22, 56, 57, 97}; printf("%dn", binary. Search(a, SIZE, 0)); printf("%dn", binary. Search(a, SIZE, -4)); printf("%dn", binary. Search(a, SIZE, 8)); printf("%dn", binary. Search(a, SIZE, 1)); printf("%dn", binary. Search(a, SIZE, -5)); printf("%dn", binary. Search(a, SIZE, 9)); printf("%dn", binary. Search(a, SIZE, 7)); 17

הבדלים מספריים 20 n 2 n lg n n 1 0 0 1 256 64 4 16 65, 536 2, 048 8 256 16, 777, 216 49, 152 12 4, 096 4, 294, 967, 296 1, 048, 565 16 65, 536 1, 099, 511, 627, 776 20, 971, 520 20 402, 653, 183 281, 474, 976, 710, 656 24 1, 048, 576 16, 777, 216

חיפוש בינארי עם מצביעים int * binary. Search (int arr [ ], int size, int quary) { int * middle; if (size == 0) return NULL; middle = arr + size/ 2; if (*middle == quary) return middle; if (*middle > quary) return binary. Search(arr, size/2, quary); else return binary. Search(arr+size/2+1, size-size/2 -1, quary); } 23

Main & Output int a [] = {-5, -3, 0, 4, 8, 11, 22, 56, 57, 97}; int * ind = binary. Search(a, SIZE, 0); if (ind != NULL) printf("%dn", ind - a); 24

חיפוש בינארי איטרטיבי int binary. Search(int arr [], int size, int quary) { int start= 0, end = size - 1; int middle; while (start <= end) { middle = (start + end) / 2; if (quary == arr [middle]) return middle; if (quary < arr [middle]) end = middle - 1; if (quary > arr [middle]) start = middle + 1; } return -1; } 25

הוספת מספר למערך ממויין /* * Requires: * 1. The elements of the array are sorted in ascending order. * 2. length < capacity * length is the current number of elements in the array * capacity is the maximum number of elements array */ void array_add(int array[], int length, int value) { int i, j; for (i = 0; i < length && array[i] <= value; i++); for (j = length; j > i; j--) array[j] = array[j - 1]; array[i] = value; } 27

Bubble Sort Example 7 2 8 5 4 2 7 5 4 8 2 5 4 7 8 2 4 5 7 8 2 7 8 5 4 2 5 7 4 8 2 4 5 7 8 2 7 5 8 4 2 5 4 7 8 (done) 2 7 5 4 8 31

Bubble Sort Code void bubble. Sort(int arr[], int size) { int i, j, tmp; for (i = size - 1; i > 0; --i) for (j = 0; j < i; ++j) if (arr[j] > arr[j+1]) { // swap tmp = arr[j]; arr[j] = arr[j+1]; arr[j+1] = tmp; } } 32

Bubble Sort Code int main() { int i, a [] = {7, 2, 8, 5, 4}; bubble. Sort(a, SIZE); for (i = 0; i < SIZE; ++i) printf("%d ", a[i]); printf("n"); return 0; } 33

מיון בועות – ניתוח סיבוכיות זמן ריצה n עבור מערך בגודל void bubble. Sort(int arr[], int size) { int i, j; for (i = size - 1; i > 0; --i) n iterations for (j = 0; j < i; ++j) i iterations if (arr[j] > arr[j+1]) { // swap tmp = arr[j]; arr[j] = arr[j+1]; constant arr[j+1] = tmp; } } (n-1 + n-2 + n-3 + …. + 1) * const ~ ½ * n 2 34

מערכים ממויינים 2 איחוד p p p 1 2 5 7 9 p q q q 3 4 6 8 10 u u u u u 1 2 3 4 5 6 7 8 9 10 38

Merge Sort (partial) Code void merge. Sort. Rec(int arr[], int start, int end) { int middle = (end - start) / 2; if ((end - start) < 2) return; merge. Sort. Rec(arr, start, middle); merge. Sort. Rec(arr, middle+1, end); merge. Arrays(arr, start, middle+1, end); } void merge. Sort(int arr [], int size) { return merge. Sort. Rec(arr, 0, size-1); } 40

דוגמא - Merge Sort 41

Bucket Sort 46