Check if two strings have a common substring
Last Updated :
27 Jan, 2023
You are given two strings str1 and str2. You have to check if the two strings share a common substring.
Examples :
Input : str1 = "HELLO"
str2 = "WORLD"
Output : YES
Explanation : The substrings "O" and
"L" are common to both str1 and str2
Input : str1 = "HI"
str2 = "ALL"
Output : NO
Explanation : Because str1 and str2
have no common substrings
A basic approach runs in O(n^2), where we compare every character of string 1 with every character of string 2 and replace every matched character with a "_" and set flag variable as true.
An efficient approach works in O(n). We basically need to check if there is a common character or not. We create a vector of size 26 for alphabets and initialize them as 0. For every character in string 1 we increment vector index of that character eg: v[s1[i]-'a']++, for every character of string 2 we check vector for the common characters if v[s2[i]-'a'] > 0 then set flag = true and v[s2[i]-'a']-- such that one character of string 2 is compared with only one character of string 1.
Implementation:
C++
// CPP program to check if two strings have
// common substring
#include <bits/stdc++.h>
using namespace std;
const int MAX_CHAR = 26;
// function to return true if strings have
// common substring and no if strings have
// no common substring
bool twoStrings(string s1, string s2) {
// vector for storing character occurrences
vector<bool> v(MAX_CHAR, 0);
// increment vector index for every
// character of str1
for (int i = 0; i < s1.length(); i++)
v[s1[i] - 'a'] = true;
// checking common substring of str2 in str1
for (int i = 0; i < s2.length(); i++)
if (v[s2[i] - 'a'])
return true;
return false;
}
// driver program
int main() {
string str1 = "hello";
string str2 = "world";
if (twoStrings(str1, str2))
cout << "Yes";
else
cout << "No";
return 0;
}
// Java program to check if two strings have
// common substring
import java.util.Arrays;
class GFG
{
static int MAX_CHAR = 26;
// function to return true if strings have
// common substring and no if strings have
// no common substring
static boolean twoStrings(String s1, String s2)
{
// vector for storing character occurrences
boolean v[]=new boolean[MAX_CHAR];
Arrays.fill(v,false);
// increment vector index for every
// character of str1
for (int i = 0; i < s1.length(); i++)
v[s1.charAt(i) - 'a'] = true;
// checking common substring of str2 in str1
for (int i = 0; i < s2.length(); i++)
if (v[s2.charAt(i) - 'a'])
return true;
return false;
}
// Driver code
public static void main (String[] args)
{
String str1 = "hello";
String str2 = "world";
if (twoStrings(str1, str2))
System.out.print("Yes");
else
System.out.print("No");
}
}
// This code is contributed by Anant Agarwal.
# Python3 code to implement the approach
# python program to check if two strings have
# common substring
MAX_CHAR = 26
# function to return true if strings have
# common substring and no if strings have
# no common substring
def twoStrings(s1, s2):
# vector for storing character occurrences
v = [0 for i in range(MAX_CHAR)]
# increment vector index for every
# character of str1
for i in range(len(s1)):
v[ord(s1[i]) - ord('a')] = True
# checking common substring of str2 in str1
for i in range(len(s2)):
if v[ord(s2[i]) - ord('a')]:
return True
return False
# driver program
str1 = "hello"
str2 = "world"
if twoStrings(str1, str2):
print("Yes")
else:
print("No")
# This code is contributed by phasing17
// C# program to check if two
// strings have common substring
using System;
class GFG
{
static int MAX_CHAR = 26;
// function to return true if strings have
// common substring and no if strings have
// no common substring
static bool twoStrings(String s1, String s2)
{
// vector for storing character occurrences
bool []v = new bool[MAX_CHAR];
// Arrays.fill(v,false);
for(int i = 0; i < MAX_CHAR; i++)
v[i]=false;
// increment vector index for
// every character of str1
for (int i = 0; i < s1.Length; i++)
v[s1[i] - 'a'] = true;
// checking common substring of str2 in str1
for (int i = 0; i < s2.Length; i++)
if (v[s2[i] - 'a'])
return true;
return false;
}
// Driver code
public static void Main ()
{
String str1 = "hello";
String str2 = "world";
if (twoStrings(str1, str2))
Console.Write("Yes");
else
Console.Write("No");
}
}
// This code is contributed by nitin mittal.
<script>
// javascript program to check if two strings have
// common substring
var MAX_CHAR = 26;
// function to return true if strings have
// common substring and no if strings have
// no common substring
function twoStrings(s1, s2) {
// vector for storing character occurrences
var v = Array(MAX_CHAR).fill(0);
// increment vector index for every
// character of str1
for (var i = 0; i < s1.length; i++)
v[s1[i] - 'a'] = true;
// checking common substring of str2 in str1
for (var i = 0; i < s2.length; i++)
if (v[s2[i] - 'a'])
return true;
return false;
}
// driver program
var str1 = "hello";
var str2 = "world";
if (twoStrings(str1, str2))
document.write( "Yes");
else
document.write("No");
// This code is contributed by rutvik_56.
</script>
Time Complexity : O(n)
Auxiliary Space: O(1)
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