Dado un texto txt[0..n-1] y un patrón pat[0..m-1] , escriba una función search(char pat[], char txt[]) que imprima todas las apariciones de pat[] en txt [] . Puede suponer que n > m.
Ejemplos:
C++
/* Following program is a C++ implementation of Rabin Karp
Algorithm given in the CLRS book */
#include <bits/stdc++.h>
using namespace std;
// d is the number of characters in the input alphabet
#define d 256
/* pat -> pattern
txt -> text
q -> A prime number
*/
void search(char pat[], char txt[], int q)
{
int M = strlen(pat);
int N = strlen(txt);
int i, j;
int p = 0; // hash value for pattern
int t = 0; // hash value for txt
int h = 1;
// The value of h would be "pow(d, M-1)%q"
for (i = 0; i < M - 1; i++)
h = (h * d) % q;
// Calculate the hash value of pattern and first
// window of text
for (i = 0; i < M; i++)
{
p = (d * p + pat[i]) % q;
t = (d * t + txt[i]) % q;
}
// Slide the pattern over text one by one
for (i = 0; i <= N - M; i++)
{
// Check the hash values of current window of text
// and pattern. If the hash values match then only
// check for characters one by one
if ( p == t )
{
/* Check for characters one by one */
for (j = 0; j < M; j++)
{
if (txt[i+j] != pat[j])
{
break;
}
}
// if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1]
if (j == M)
cout<<"Pattern found at index "<< i<<endl;
}
// Calculate hash value for next window of text: Remove
// leading digit, add trailing digit
if ( i < N-M )
{
t = (d*(t - txt[i]*h) + txt[i+M])%q;
// We might get negative value of t, converting it
// to positive
if (t < 0)
t = (t + q);
}
}
}
/* Driver code */
int main()
{
char txt[] = "GEEKS FOR GEEKS";
char pat[] = "GEEK";
//we mod to avoid overflowing of value but we should take as big q as possible to avoid the collison
int q =INT_MAX;
// Function Call
search(pat, txt, q);
return 0;
}
// This is code is contributed by rathbhupendra
C
/* Following program is a C implementation of Rabin Karp
Algorithm given in the CLRS book */
#include<stdio.h>
#include<string.h>
// d is the number of characters in the input alphabet
#define d 256
/* pat -> pattern
txt -> text
q -> A prime number
*/
void search(char pat[], char txt[], int q)
{
int M = strlen(pat);
int N = strlen(txt);
int i, j;
int p = 0; // hash value for pattern
int t = 0; // hash value for txt
int h = 1;
// The value of h would be "pow(d, M-1)%q"
for (i = 0; i < M-1; i++)
h = (h*d)%q;
// Calculate the hash value of pattern and first
// window of text
for (i = 0; i < M; i++)
{
p = (d*p + pat[i])%q;
t = (d*t + txt[i])%q;
}
// Slide the pattern over text one by one
for (i = 0; i <= N - M; i++)
{
// Check the hash values of current window of text
// and pattern. If the hash values match then only
// check for characters one by one
if ( p == t )
{
/* Check for characters one by one */
for (j = 0; j < M; j++)
{
if (txt[i+j] != pat[j])
break;
}
// if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1]
if (j == M)
printf("Pattern found at index %d \n", i);
}
// Calculate hash value for next window of text: Remove
// leading digit, add trailing digit
if ( i < N-M )
{
t = (d*(t - txt[i]*h) + txt[i+M])%q;
// We might get negative value of t, converting it
// to positive
if (t < 0)
t = (t + q);
}
}
}
/* Driver Code */
int main()
{
char txt[] = "GEEKS FOR GEEKS";
char pat[] = "GEEK";
// A prime number
int q = 101;
// function call
search(pat, txt, q);
return 0;
}
Java
// Following program is a Java implementation
// of Rabin Karp Algorithm given in the CLRS book
public class Main
{
// d is the number of characters in the input alphabet
public final static int d = 256;
/* pat -> pattern
txt -> text
q -> A prime number
*/
static void search(String pat, String txt, int q)
{
int M = pat.length();
int N = txt.length();
int i, j;
int p = 0; // hash value for pattern
int t = 0; // hash value for txt
int h = 1;
// The value of h would be "pow(d, M-1)%q"
for (i = 0; i < M-1; i++)
h = (h*d)%q;
// Calculate the hash value of pattern and first
// window of text
for (i = 0; i < M; i++)
{
p = (d*p + pat.charAt(i))%q;
t = (d*t + txt.charAt(i))%q;
}
// Slide the pattern over text one by one
for (i = 0; i <= N - M; i++)
{
// Check the hash values of current window of text
// and pattern. If the hash values match then only
// check for characters one by one
if ( p == t )
{
/* Check for characters one by one */
for (j = 0; j < M; j++)
{
if (txt.charAt(i+j) != pat.charAt(j))
break;
}
// if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1]
if (j == M)
System.out.println("Pattern found at index " + i);
}
// Calculate hash value for next window of text: Remove
// leading digit, add trailing digit
if ( i < N-M )
{
t = (d*(t - txt.charAt(i)*h) + txt.charAt(i+M))%q;
// We might get negative value of t, converting it
// to positive
if (t < 0)
t = (t + q);
}
}
}
/* Driver Code */
public static void main(String[] args)
{
String txt = "GEEKS FOR GEEKS";
String pat = "GEEK";
// A prime number
int q = 101;
// Function Call
search(pat, txt, q);
}
}
// This code is contributed by nuclode
Python3
# Following program is the python implementation of
# Rabin Karp Algorithm given in CLRS book
# d is the number of characters in the input alphabet
d = 256
# pat -> pattern
# txt -> text
# q -> A prime number
def search(pat, txt, q):
M = len(pat)
N = len(txt)
i = 0
j = 0
p = 0 # hash value for pattern
t = 0 # hash value for txt
h = 1
# The value of h would be "pow(d, M-1)%q"
for i in range(M-1):
h = (h*d)%q
# Calculate the hash value of pattern and first window
# of text
for i in range(M):
p = (d*p + ord(pat[i]))%q
t = (d*t + ord(txt[i]))%q
# Slide the pattern over text one by one
for i in range(N-M+1):
# Check the hash values of current window of text and
# pattern if the hash values match then only check
# for characters one by one
if p==t:
# Check for characters one by one
for j in range(M):
if txt[i+j] != pat[j]:
break
else: j+=1
# if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1]
if j==M:
print ("Pattern found at index " + str(i))
# Calculate hash value for next window of text: Remove
# leading digit, add trailing digit
if i < N-M:
t = (d*(t-ord(txt[i])*h) + ord(txt[i+M]))%q
# We might get negative values of t, converting it to
# positive
if t < 0:
t = t+q
# Driver Code
txt = "GEEKS FOR GEEKS"
pat = "GEEK"
# A prime number
q = 101
# Function Call
search(pat,txt,q)
# This code is contributed by Bhavya Jain
C#
// Following program is a C# implementation
// of Rabin Karp Algorithm given in the CLRS book
using System;
public class GFG
{
// d is the number of characters in the input alphabet
public readonly static int d = 256;
/* pat -> pattern
txt -> text
q -> A prime number
*/
static void search(String pat, String txt, int q)
{
int M = pat.Length;
int N = txt.Length;
int i, j;
int p = 0; // hash value for pattern
int t = 0; // hash value for txt
int h = 1;
// The value of h would be "pow(d, M-1)%q"
for (i = 0; i < M-1; i++)
h = (h*d)%q;
// Calculate the hash value of pattern and first
// window of text
for (i = 0; i < M; i++)
{
p = (d*p + pat[i])%q;
t = (d*t + txt[i])%q;
}
// Slide the pattern over text one by one
for (i = 0; i <= N - M; i++)
{
// Check the hash values of current window of text
// and pattern. If the hash values match then only
// check for characters one by one
if ( p == t )
{
/* Check for characters one by one */
for (j = 0; j < M; j++)
{
if (txt[i+j] != pat[j])
break;
}
// if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1]
if (j == M)
Console.WriteLine("Pattern found at index " + i);
}
// Calculate hash value for next window of text: Remove
// leading digit, add trailing digit
if ( i < N-M )
{
t = (d*(t - txt[i]*h) + txt[i+M])%q;
// We might get negative value of t, converting it
// to positive
if (t < 0)
t = (t + q);
}
}
}
/* Driver Code */
public static void Main()
{
String txt = "GEEKS FOR GEEKS";
String pat = "GEEK";
// A prime number
int q = 101;
// Function Call
search(pat, txt, q);
}
}
// This code is contributed by PrinciRaj19992
PHP
<?php
// Following program is a PHP
// implementation of Rabin Karp
// Algorithm given in the CLRS book
// d is the number of characters
// in the input alphabet
$d = 256;
/* pat -> pattern
txt -> text
q -> A prime number
*/
function search($pat, $txt, $q)
{
$M = strlen($pat);
$N = strlen($txt);
$i; $j;
$p = 0; // hash value
// for pattern
$t = 0; // hash value
// for txt
$h = 1;
$d =1;
// The value of h would
// be "pow(d, M-1)%q"
for ($i = 0; $i < $M - 1; $i++)
$h = ($h * $d) % $q;
// Calculate the hash value
// of pattern and first
// window of text
for ($i = 0; $i < $M; $i++)
{
$p = ($d * $p + $pat[$i]) % $q;
$t = ($d * $t + $txt[$i]) % $q;
}
// Slide the pattern over
// text one by one
for ($i = 0; $i <= $N - $M; $i++)
{
// Check the hash values of
// current window of text
// and pattern. If the hash
// values match then only
// check for characters one
// by one
if ($p == $t)
{
// Check for characters
// one by one
for ($j = 0; $j < $M; $j++)
{
if ($txt[$i + $j] != $pat[$j])
break;
}
// if p == t and pat[0...M-1] =
// txt[i, i+1, ...i+M-1]
if ($j == $M)
echo "Pattern found at index ",
$i, "\n";
}
// Calculate hash value for
// next window of text:
// Remove leading digit,
// add trailing digit
if ($i < $N - $M)
{
$t = ($d * ($t - $txt[$i] *
$h) + $txt[$i +
$M]) % $q;
// We might get negative
// value of t, converting
// it to positive
if ($t < 0)
$t = ($t + $q);
}
}
}
// Driver Code
$txt = "GEEKS FOR GEEKS";
$pat = "GEEK";
// A prime number
$q = 101;
// Function Call
search($pat, $txt, $q);
// This code is contributed
// by ajit
?>
Javascript
<script>
// Following program is a Javascript implementation
// of Rabin Karp Algorithm given in the CLRS book
// d is the number of characters in
// the input alphabet
let d = 256;
/* pat -> pattern
txt -> text
q -> A prime number
*/
function search(pat, txt, q)
{
let M = pat.length;
let N = txt.length;
let i, j;
// Hash value for pattern
let p = 0;
// Hash value for txt
let t = 0;
let h = 1;
// The value of h would be "pow(d, M-1)%q"
for(i = 0; i < M - 1; i++)
h = (h * d) % q;
// Calculate the hash value of pattern and
// first window of text
for(i = 0; i < M; i++)
{
p = (d * p + pat[i].charCodeAt()) % q;
t = (d * t + txt[i].charCodeAt()) % q;
}
// Slide the pattern over text one by one
for(i = 0; i <= N - M; i++)
{
// Check the hash values of current
// window of text and pattern. If the
// hash values match then only
// check for characters one by one
if (p == t)
{
/* Check for characters one by one */
for(j = 0; j < M; j++)
{
if (txt[i+j] != pat[j])
break;
}
// if p == t and pat[0...M-1] =
// txt[i, i+1, ...i+M-1]
if (j == M)
document.write("Pattern found at index " +
i + "<br/>");
}
// Calculate hash value for next window
// of text: Remove leading digit, add
// trailing digit
if (i < N - M)
{
t = (d * (t - txt[i].charCodeAt() * h) +
txt[i + M].charCodeAt()) % q;
// We might get negative value of t,
// converting it to positive
if (t < 0)
t = (t + q);
}
}
}
// Driver code
let txt = "GEEKS FOR GEEKS";
let pat = "GEEK";
// A prime number
let q = 101;
// Function Call
search(pat, txt, q);
// This code is contributed by target_2
</script>
Publicación traducida automáticamente
Artículo escrito por GeeksforGeeks-1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA