String dada str . La tarea es encontrar la substring más larga que es un prefijo, un sufijo y una substring de la string dada, str. Si no existe tal string, imprima -1 .
Ejemplos:
Entrada: str = “geeksisforgeeksinplatformgeeks”
Salida: geeks
Entrada: str = “fixprefixsuffix”
Salida: fix
Nota: El Set-1 de este artículo se adjunta aquí .
Enfoque:
la implementación utiliza el algoritmo BIT y Z. Aprenda más sobre ellos de esto y esto .
- Primero estamos calculando la array Z usando el algoritmo Z.
- Actualice los valores en la array de bits en 1 desde el índice z[i].
- Consultando la substring de longitud máxima necesaria usando la función pref.
- Si len es 0, entonces dicha substring no es posible a partir de la string dada.
A continuación se muestra el enfoque de implementación:
C++
// C++ program to find that
// substring which is its
// suffix prefix and also
// found somewhere in between
#include <bits/stdc++.h>
using namespace std;
// Z-algorithm function
vector<int> z_function(string s)
{
int n = s.size();
vector<int> z(n);
for (int i = 1, l = 0,
r = 0;
i < n;
i++) {
if (i <= r)
z[i] = min(r - i + 1,
z[i - l]);
while (i + z[i] < n
&& s[z[i]] == s[i + z[i]])
z[i]++;
if (i + z[i] - 1 > r)
l = i, r = i + z[i] - 1;
}
return z;
}
int n, len = 0;
// BIT array
int bit[1000005];
string s;
vector<int> z;
map<int, int> m;
// bit update function which
// updates values from index
// "idx" to last by value "val"
void update(int idx, int val)
{
if (idx == 0)
return;
while (idx <= n) {
bit[idx] += val;
idx += (idx & -idx);
}
}
// Query function in bit
int pref(int idx)
{
int ans = 0;
while (idx > 0) {
ans += bit[idx];
idx -= (idx & -idx);
}
return ans;
}
// Driver Code
int main()
{
s = "geeksisforgeeksinplatformgeeks";
n = s.size();
// Making the z array
z = z_function(s);
// update in the bit array from
// index z[i] by increment of 1
for (int i = 1; i < n; i++) {
update(z[i], 1);
}
for (int i = n - 1; i > 1; i--) {
// if the value in z[i] is
// not equal to (n-i) then no
// need to move further
if (z[i] != (n - i))
continue;
// queryng for the maximum
// length substring from
// bit array
if (pref(n) - pref(z[i] - 1) >= 2) {
len = max(len, z[i]);
}
}
if (!len)
cout << "-1";
else
cout << s.substr(0, len);
return 0;
}
Java
// Java program to find that
// substring which is its
// suffix prefix and also
// found somewhere in between
class GFG
{
// Z-algorithm function
static int[] z_function(char []s)
{
int n = s.length;
int []z = new int[n];
for (int i = 1, l = 0, r = 0;
i < n; i++)
{
if (i <= r)
z[i] = Math.min(r - i + 1,
z[i - l]);
while (i + z[i] < n &&
s[z[i]] == s[i + z[i]])
z[i]++;
if (i + z[i] - 1 > r)
{
l = i; r = i + z[i] - 1;
}
}
return z;
}
static int n, len = 0;
// BIT array
static int []bit = new int[1000005];
static String s;
static int[] z;
// bit update function which
// updates values from index
// "idx" to last by value "val"
static void update(int idx, int val)
{
if (idx == 0)
return;
while (idx <= n)
{
bit[idx] += val;
idx += (idx & -idx);
}
}
// Query function in bit
static int pref(int idx)
{
int ans = 0;
while (idx > 0)
{
ans += bit[idx];
idx -= (idx & -idx);
}
return ans;
}
// Driver Code
public static void main(String[] args)
{
s = "geeksisforgeeksinplatformgeeks";
z = new int[s.length()];
n = s.length();
// Making the z array
z = z_function(s.toCharArray());
// update in the bit array from
// index z[i] by increment of 1
for (int i = 1; i < n; i++)
{
update(z[i], 1);
}
for (int i = n - 1; i > 1; i--)
{
// if the value in z[i] is
// not equal to (n-i) then no
// need to move further
if (z[i] != (n - i))
continue;
// queryng for the maximum
// length substring from
// bit array
if (pref(n) - pref(z[i] - 1) >= 2)
{
len = Math.max(len, z[i]);
}
}
if (len == 0)
System.out.println("-1");
else
System.out.println(s.substring(0, len));
}
}
// This code is contributed
// by PrinciRaj1992
Python3
# Python3 program to find that # substring which is its # suffix prefix and also # found somewhere in between # Z-algorithm function def z_function(s): global z, n n = len(s) z = [0] * n l, r = 0, 0 for i in range(1, n): if i <= r: z[i] = min(r - i + 1, z[i - 1]) while (i + z[i] < n and s[z[i]] == s[i + z[i]]): z[i] += 1 if (i + z[i] - 1 > r): l = i r = i + z[i] - 1 return z # bit update function which # updates values from index # "idx" to last by value "val" def update(idx, val): global bit if idx == 0: return while idx <= n: bit[idx] += val idx += (idx & -idx) # Query function in bit def pref(idx): global bit ans = 0 while idx > 0: ans += bit[idx] idx -= (idx & -idx) return ans # Driver Code if __name__ == "__main__": n = 0 length = 0 # BIT array bit = [0] * 1000005 z = [] m = dict() s = "geeksisforgeeksinplatformgeeks" # Making the z array z = z_function(s) # update in the bit array from # index z[i] by increment of 1 for i in range(1, n): update(z[i], 1) for i in range(n - 1, 1, -1): # if the value in z[i] is # not equal to (n-i) then no # need to move further if z[i] != n - i: continue # queryng for the maximum # length substring from # bit array if (pref(n) - pref(z[i] - 1)) >= 2: length = max(length, z[i]) if not length: print(-1) else: print(s[:length]) # This code is contributed by # sanjeev2552
C#
// C# program to find that
// substring which is its
// suffix prefix and also
// found somewhere in between
using System;
class GFG
{
// Z-algorithm function
static int[] z_function(char []s)
{
int n = s.Length;
int []z = new int[n];
for (int i = 1, l = 0, r = 0;
i < n; i++)
{
if (i <= r)
z[i] = Math.Min(r - i + 1,
z[i - l]);
while (i + z[i] < n &&
s[z[i]] == s[i + z[i]])
z[i]++;
if (i + z[i] - 1 > r)
{
l = i; r = i + z[i] - 1;
}
}
return z;
}
static int n, len = 0;
// BIT array
static int []bit = new int[1000005];
static String s;
static int[] z;
// bit update function which
// updates values from index
// "idx" to last by value "val"
static void update(int idx, int val)
{
if (idx == 0)
return;
while (idx <= n)
{
bit[idx] += val;
idx += (idx & -idx);
}
}
// Query function in bit
static int pref(int idx)
{
int ans = 0;
while (idx > 0)
{
ans += bit[idx];
idx -= (idx & -idx);
}
return ans;
}
// Driver Code
public static void Main(String[] args)
{
s = "geeksisforgeeksinplatformgeeks";
z = new int[s.Length];
n = s.Length;
// Making the z array
z = z_function(s.ToCharArray());
// update in the bit array from
// index z[i] by increment of 1
for (int i = 1; i < n; i++)
{
update(z[i], 1);
}
for (int i = n - 1; i > 1; i--)
{
// if the value in z[i] is
// not equal to (n-i) then no
// need to move further
if (z[i] != (n - i))
continue;
// queryng for the maximum
// length substring from
// bit array
if (pref(n) - pref(z[i] - 1) >= 2)
{
len = Math.Max(len, z[i]);
}
}
if (len == 0)
Console.WriteLine("-1");
else
Console.WriteLine(s.Substring(0, len));
}
}
// This code is contributed by PrinciRaj1992
Producción:
geeks
Complejidad del tiempo: O(N)