Lecture 9

Searching and Sorting

List Operations

· Search for a given item

· Sort the list

· Insert item

· Delete item

· Print List

Sequential Search

int seqSearch(const int list[], int listLength, int searchItem)

[

int loc;

bool found=false;

loc=0;

while(loc<listLength && !found);

if (list[loc]==searchItem)

found=true;

else

loc++;

if (found)

return loc;

else

return)1;

Problem when item is at bottom long search

Solution is to sort items in order and then do a quicker search

Illustrate how the Bubble Sort (Compare and Swap) algorithm would place the following numbers into order

.

Iterations

1 Largest to bottom	2 Next larger	3 Next larger	4 Next larger
89 15 15 15 15 ‡	15 15 15 15 ‡
‡ 15 89 78 78 78 ‡	‡ 78 78 45 45 ‡
‡ 78 78 89 45 45 ‡	‡ 45 45 78 67 ‡
‡ 45 45 45 89 67 ‡	‡ 67 67 67 78
‡ 67 67 67 67 89	89 89 89 89

void bubbleSort(int list[], int length)

{

int temp;

int iteration;

int index;

for (iteration=1; iteration<length; iteration++)

{

for (index=0; index<length-iteration; index++)

if (list[index]>list[index+1])

{

temp=list[index];

list[index]=list[index=1];

list{index+1]=temp;

}

Can now do Binary Search

· Check midpoint of list

· Item greater or less then midpoint

· Remove the non contained half

· Check again midpoint of retained half

· Proceed in this manner until found

int binarySearch(Const int list[], int listLength, int searchItemJJJJJJ)

{

int first=0;

int last=listLength-1;

int mid;

bool found=false;

while(first<=last &&!found)

{

mid=(first+last)/2;

if(list[mid]==searchItem)

found=true;

else if (list[mid>searchItem)

last=mid-1;

else

first=mid+1;

}

if (found)

return mid;

else

return -1;

}