Sub-strings having exactly k characters that have ASCII value greater than p

Given a string ‘str’, two integers ‘k’ and ‘p’. The task is to count all the sub-strings of ‘str’ having exactly ‘k’ characters that have ASCII value greater than ‘p’.

Examples:

Input: str = “abcd”, k=2, p=98
Output: 3
Only the characters ‘c’ and ‘d’ have ASCII values greater than 98,
And, the sub-strings containing them are “abcd”, “bcd” and “cd”.

Input: str = “sabrcd”, k=5, p=80
Output: 2



Approach: We just need to iterate over all indices and take all possible length sub-strings and then just check whether the sub-string has exactly ‘k’ characters that have ASCII value greater than ‘p’.

Typecasting a character to int will give us it’s ASCII value i.e. int ascii = (int) char.

Below is the implementation of the above approach:

C++

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function that checks if
// the string contain exactly
// K characters having ASCII
// value greater than p
bool isValidSubString(string r, int K, int p)
{
    int c = 0;
  
    for (int i = 0; i < r.length(); i++) {
  
        // if ASCII value is
        // greater than 'p'
        if ((int)r[i] > p)
            c++;
    }
  
    // if count of satisfying
    // characters is equal to 'K'
    // then return true
    if (c == K)
        return true;
  
    // otherwise return false
    else
        return false;
}
  
// function to count sub-strings
void countSubStrings(string s, int K, int p)
{
    // length of the string
    int l = s.length();
  
    // count of sub-strings
    int count = 0;
  
    // 'i' is the starting
    // index for the sub-string
    for (int i = 0; i < l; i++) {
  
        // 'j' is the no. of characters
        // to include in the sub-string
        for (int j = K; (i + j) <= l; j++) {
            string r = s.substr(i, j);
  
            // check if the sub-string
            // satisfies the condition
            if (isValidSubString(r, K, p))
                count++;
        }
    }
  
    cout << count << "\n";
}
  
// Driver code
int main()
{
  
    string s = "abepztydba";
    int K = 4;
    int p = 110;
  
    countSubStrings(s, K, p);
  
    return 0;
}

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Python3

# Python3 implementation of the approach

# Function that checks if the string
# contain exactly K characters having
# ASCII value greater than p
def isValidSubString(r, K, p):

c = 0
for i in range(0, len(r)):

# if ASCII value is
# greater than ‘p’
if ord(r[i]) > p:
c += 1

# if count of satisfying
# characters is equal to ‘K’
# then return true
if c == K:
return True

# otherwise return false
else:
return False

# function to count sub-strings
def countSubStrings(s, K, p):

# length of the string
l = len(s)

# count of sub-strings
count = 0

# ‘i’ is the starting
# index for the sub-string
for i in range(0, l):

# ‘j’ is the no. of characters
# to include in the sub-string
for j in range(K, l – i + 1):
r = s[i:i + j]

# check if the sub-string
# satisfies the condition
if isValidSubString(r, K, p) == True:
count += 1

print(count)

# Driver code
if __name__ == “__main__”:

s = “abepztydba”
K, p = 4, 110

countSubStrings(s, K, p)

# This code is contributed by Rituraj Jain

Output:

16


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Improved By : rituraj_jain



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