Given a string S and an array arr[] of phrases, the duty is to return the quantity of phrases from the array which is a subsequence of S.
Examples:
Enter: S = “programming”, arr[] = {“promenade”, “amin”, “proj”}
Output: 2
Clarification: “promenade” and “amin” are subsequence of S whereas “proj” just isn’t)Enter: S = “geeksforgeeks”, arr[] = {“gfg”, “geek”, “geekofgeeks”, “for”}
Output: 3
Clarification:” gfg”, “geek” and “for” are subsequences of S whereas “geekofgeeks” just isn’t.
Naive Method: The fundamental method to resolve the issue is as follows:
The concept is to examine all strings within the phrases array arr[] that are subsequences of S by recursion.
Beneath is the implementation of the above strategy:
C++
// C++ code for the above strategy:
#embrace <bits/stdc++.h>
utilizing namespace std;
bool isSubsequence(string& str1, int m, string& str2, int n)
{
if (m == 0)
return true;
if (n == 0)
return false;
// If final characters of two strings
// are matching
if (str1[m - 1] == str2[n - 1])
return isSubsequence(str1, m - 1, str2, n - 1);
// If final characters aren't matching
return isSubsequence(str1, m, str2, n - 1);
}
// Perform to depend variety of phrases that
// are subsequence of given string S
int countSubsequenceWords(string s, vector<string>& arr)
{
int n = arr.dimension();
int m = s.size();
int res = 0;
for (int i = 0; i < n; i++) {
if (isSubsequence(arr[i], arr[i].dimension(), s, m)) {
res++;
}
}
return res;
}
// Driver Code
int predominant()
{
string S = "geeksforgeeks";
vector<string> arr
= { "geek", "for", "geekofgeeks", "gfg" };
// Funtion name
cout << countSubsequenceWords(S, arr) << "n";
return 0;
}
Time Complexity: O(m*n)
Auxiliary House: O(m) for recursion stack area
Environment friendly Method: The above strategy will be optimized based mostly on the next thought:
- Map the index of characters of the given string to the respective characters array.
- Initialize the ans with the scale of arr.
- Iterate over all of the phrases in arr one after the other.
- Iterate over every character.
- Discover strictly higher index than prevIndex in dict.
- If the strictly higher ingredient just isn’t discovered, it means the present phrase just isn’t a subsequence of the given string, so lower res by 1.
- Else replace prevIndex.
- After iterating over all of the phrases, return ans.
Beneath is the implementation of the above strategy:
C++
// C++ code for the above strategy:
#embrace <bits/stdc++.h>
utilizing namespace std;
// Perform to depend variety of phrases that
// are subsequence of given string S
int countSubsequenceWords(string s, vector<string>& arr)
{
unordered_map<char, vector<int> > dict;
// Mapping index of characters of given
// string to respective characters
for (int i = 0; i < s.size(); i++) {
dict[s[i]].push_back(i);
}
// Initializing res with dimension of arr
int res = arr.dimension();
for (auto phrase : arr) {
// Index the place final character
// is discovered
int prevIndex = -1;
for (int j = 0; j < phrase.dimension(); j++) {
// Looking for strictly
// higher ingredient than prev
// utilizing binary search
auto x = upper_bound(dict[word[j]].start(),
dict[word[j]].finish(),
prevIndex);
// If strictly higher index
// not discovered, the phrase can't
// be subsequence of string s
if (x == dict[word[j]].finish()) {
res--;
break;
}
// Else, replace the prevIndex
else {
prevIndex = *x;
}
}
}
return res;
}
// Driver Code
int predominant()
{
string S = "geeksforgeeks";
vector<string> arr
= { "geek", "for", "geekofgeeks", "gfg" };
// Perform name
cout << countSubsequenceWords(S, arr) << "n";
return 0;
}
Time Complexity: O( m * s * log(n) ), the place m is the size of the given string, s is the max size of the phrase of arr and n is the size of arr
Auxiliary House: O(n)
