Matakuliah
Tahun
Versi
: T0016/Algoritma dan Pemrograman
: 2005
: versi 2
Pertemuan 24
Teknik Searching
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Menjelaskan berbagai teknik searching
2
Outline Materi
• Sequential search
• Binary Search
• Interpolation search
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Sequential Search
In computer science, linear search is a
search algorithm , also known as
sequential search, that is suitable for
searching a set of data for a particular
value.
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Linear search
public int sequentialSearch(int arr[], int key) {
for (int k = 0; k < arr.length; k++)
if (arr[k] == key)
return k;
return -1; // Failure
} // sequentialSearch()
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Binary Search
• Binary Search will search a sorted array by
repeatedly dividing the search interval in half.
Begin with an interval covering the whole array.
• If the value of the search key is less than the
item in the middle of the interval, narrow the
interval to the lower half. Otherwise narrow it to
the upper half. Repeatedly check until the value
is found or the interval is empty.
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• Finding the middle is often coded as
mid = (high + low)/2;
• This overflows if high and low are close to the
largest expressible integer. The following gives
the same result and never overflows, if high and
low are non-negative.
mid = low + (high - low)/2;
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Algoritma Binary Search
function binarySearch(a, value, left, right)
while left ≤ right
mid := floor((left+right)/2)
if a[mid] = value
return mid
if value < a[mid]
right := mid-1
else if value > a[mid]
left := mid+1
return not found
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Interpolation Search
• An approximate location is interpolated
from the first and last items of a sorted
array, then a linear search finds the actual
location.
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Interpolation Search
function search( key : typekey; var r : dataarray ) : integer;
var high, j, low : integer;
begin low := 1; high := n;
while (r[high].k >= key) and (key > r[low].k)
do begin
j := trunc( (key-r[low].k) / (r[high].k-r[low].k) * (high-low) ) + low;
if key > r[j].k then low := j+1
else if key < r[j].k then high := j-1
else low := j end;
if r[low].k = key then
search := low {*** found(r[low]) ***}
else search := -1;
{*** notfound(key) ***} end;
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Penutup
• Linear search merupakan algoritma
pencarian yang sangat mudah, namun
menjadi sangat lama jika datanya sangat
banyak.
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