C++ Programming Code Examples
C++ > Strings Code Examples
C++ Program to Implement Z-Algorithm
/* C++ Program to Implement Z-Algorithm
This C++ Program demonstrates the implementation of Z-Algorithm. */
#include <iostream>
#include <cstring>
#include <vector>
using namespace std;
bool zAlgorithm(string pattern, string target)
{
string s = pattern + '$' + target;
int n = s.length();
vector<int> z(n, 0);
int goal = pattern.length();
int r = 0, l = 0, i;
for (int k = 1; k < n; k++)
{
if (k > r)
{
for (i = k; i < n && s[i] == s[i - k]; i++);
if (i > k)
{
z[k] = i - k;
l = k;
r = i - 1;
}
}
else
{
int kt = k - l, b = r - k + 1;
if (z[kt] > b)
{
for (i = r + 1; i < n && s[i] == s[i - k]; i++);
z[k] = i - k;
l = k;
r = i - 1;
}
}
if (z[k] == goal)
return true;
}
return false;
}
int main()
{
string tar = "Happy Codings - C++ Programming Language Code Examples";
string pat = "Happy";
if (zAlgorithm(pat, tar))
cout<<"'"<<pat<<"' found in string '"<<tar<<"'"<<endl;
else
cout<<"'"<<pat<<"' not found in string '"<<tar<<"'"<<endl;
pat = "Happy Codings";
if (zAlgorithm(pat, tar))
cout<<"'"<<pat<<"' found in string '"<<tar<<"'"<<endl;
else
cout<<"'"<<pat<<"' not found in string '"<<tar<<"'"<<endl;
return 0;
}
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