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Count strings that end with the given pattern in C++
We are given an array of strings str[] and a pattern string pat. The goal is to find the string elements of str[] that have pattern pat at the end.
We will traverse each string of str and compare last characters with pat. If they match increment
Let’s understand with examples.
Input
str[]={ “kittens”, “hens”, “deers”, “dogs” } pat=”ens”Output
Strings that end with given pattern: 2
Explanation
Strings “kitt-ens” and “h-ens” end with “ens”.
Input
str[]={ “tickets”, “wickets”, “bats”, “cricket” } pat=”et”Output
Strings that end with given pattern: 1
Explanation
Strings “wick-et” ends with “et”.
Approach used in the below program is as follows
We string array str[] and a pattern string pat.
N is no of strings in str[].
Function endPattern(string str[], int n, string ptr) returns the count of strings in str that end with given pattern
Take the initial variable count as 0.
Traverse using for loop from i=1 to i<n
Take each string str[i] as s. Let slen be s.length().
Take plen=ptr.lenght(). Take flag=1.
Now decreent plen and slen by 1 to get the last indexes of string s and pattern ptr.
Using while loop check until plen>=0.
If any s[slen]!=ptr[plen]. Set flag=0 and break the loop. Otherwise decrement plen and slen to check the next character from end.
After the while ends, if flag is still 1 then increment count as ptr occurs in s.
Return count after end of all loops which is count of strings ending with given pattern.
Example
#include <bits/stdc++.h>
using namespace std;
int endPattern(string str[], int n, string ptr){
int count=0;
for(int i=0;i<n;i++){
string s=str[i];
int slen=s.length();
int plen=ptr.length();
int flag=1;
slen--; //last index
plen--;
while(plen>=0){
if(ptr[plen]!=s[slen]){
flag=0;
break;
}
plen--;
slen--;
}
if(flag==1)
{ count++; }
}
return count;
}
int main(){
string patrn = "pes";
int N = 4;
string str[] = { "stripes", "cars", "ripes", "pipes" };
cout <<"Strings that end with given pattern: "<<endPattern(str,N,patrn);
return 0;
}Output
If we run the above code it will generate the following output −
Strings that end with given pattern: 3
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