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Count occurrences of substring X before every occurrence of substring Y in a given string
• Last Updated : 26 May, 2021

Given three strings S, X, and Y consisting of N, A, and B characters respectively, the task is to find the number of occurrences of the substring X before every occurrence of the substring Y in the given string S.

Examples:

Input S = ”abcdefdefabc”, X = ”def”, Y = ”abc”
Output: 0 2
Explanation:
First occurence of Y(= “abc”): No of occurrences of X(= “def”) = 0.
Second occurrence of Y: No of occurrences of X = 0.

Input: S = ”accccbbbbbbaaa”, X = ”a”, Y = ”b”
Output: 0 6 6 6

Approach: Follow the steps below to solve the problem:

• Initialize a variable, say count, that stores the total number occurrences of X.
• Traverse the given string S and perform the following steps:
• If the substring over the range [i, B] is equal to Y, then increment count by 1.
• If the substring over the range [i, A] is equal to X, then print the value of count as the resultant count of the string Y before the current occurrence of the string X.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to count occurrences of``// the string Y in the string S for``// every occurrence of X in S``void` `countOccurrences(string S,``                      ``string X,``                      ``string Y)``{``    ``// Stores the count of``    ``// occurrences of X``    ``int` `count = 0;` `    ``// Stores the lengths of the``    ``// three strings``    ``int` `N = S.length(), A = X.length();``    ``int` `B = Y.length();` `    ``// Traverse the string S``    ``for` `(``int` `i = 0; i < N; i++) {` `        ``// If the current substring``        ``// is Y, then increment the``        ``// value of count by 1``        ``if` `(S.substr(i, B) == Y)``            ``count++;` `        ``// If the current substring``        ``// is X, then print the count``        ``if` `(S.substr(i, A) == X)``            ``cout << count << ``" "``;``    ``}``}` `// Driver Code``int` `main()``{``    ``string S = ``"abcdefdefabc"``;``    ``string X = ``"abc"``;``    ``string Y = ``"def"``;``    ``countOccurrences(S, X, Y);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.io.*;``import` `java.lang.*;``import` `java.util.*;` `public` `class` `GFG {` `    ``// Function to count occurrences of``    ``// the string Y in the string S for``    ``// every occurrence of X in S``    ``static` `void` `countOccurrences(String S, String X,``                                 ``String Y)``    ``{``        ``// Stores the count of``        ``// occurrences of X``        ``int` `count = ``0``;` `        ``// Stores the lengths of the``        ``// three strings``        ``int` `N = S.length(), A = X.length();``        ``int` `B = Y.length();` `        ``// Traverse the string S``        ``for` `(``int` `i = ``0``; i < N; i++) {` `            ``// If the current substring``            ``// is Y, then increment the``            ``// value of count by 1``            ``if` `(S.substring(i, Math.min(N, i + B))``                    ``.equals(Y))``                ``count++;` `            ``// If the current substring``            ``// is X, then print the count``            ``if` `(S.substring(i, Math.min(N, i + A))``                    ``.equals(X))``                ``System.out.print(count + ``" "``);``        ``}``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``String S = ``"abcdefdefabc"``;``        ``String X = ``"abc"``;``        ``String Y = ``"def"``;``        ``countOccurrences(S, X, Y);``    ``}``}` `// This code is contributed by Kingash.`

## Python3

 `# Python program for the above approach` `# Function to count occurrences of``# the string Y in the string S for``# every occurrence of X in S``def` `countOccurrences(S, X, Y):``  ` `    ``# Stores the count of``    ``# occurrences of X``    ``count ``=` `0` `    ``# Stores the lengths of the``    ``# three strings``    ``N ``=` `len``(S)``    ``A ``=` `len``(X)``    ``B ``=` `len``(Y)` `    ``# Traverse the string S``    ``for`  `i ``in` `range``( ``0``,  N):``      ` `        ``# If the current substring``        ``# is Y, then increment the``        ``# value of count by 1``        ``if` `(S[i: i``+``B] ``=``=` `Y):``            ``count``+``=``1` `        ``# If the current substring``        ``# is X, then print the count``        ``if` `(S[i:i``+``A] ``=``=` `X):``            ``print``(count, end ``=` `" "``)``            ` `# Driver Code``S ``=` `"abcdefdefabc"``X ``=` `"abc"``Y ``=` `"def"``countOccurrences(S, X, Y)` `# This code is contributed by rohitsingh07052.`

## C#

 `// C# program for the above approach``using` `System;``public` `class` `GFG {` `    ``// Function to count occurrences of``    ``// the string Y in the string S for``    ``// every occurrence of X in S``    ``static` `void` `countOccurrences(``string` `S, ``string` `X,``                                 ``string` `Y)``    ``{``        ``// Stores the count of``        ``// occurrences of X``        ``int` `count = 0;` `        ``// Stores the lengths of the``        ``// three strings``        ``int` `N = S.Length, A = X.Length;``        ``int` `B = Y.Length;``        ``int` `P = Math.Min(A, Math.Min(N, B));` `        ``// Traverse the string S``        ``for` `(``int` `i = 0; i < N - P + 1; i++) {` `            ``// If the current substring``            ``// is Y, then increment the``            ``// value of count by 1` `            ``if` `(S.Substring(i, Math.Min(N, B)).Equals(Y))``                ``count++;` `            ``// If the current substring``            ``// is X, then print the count``            ``if` `(S.Substring(i, Math.Min(N, A)).Equals(X))``                ``Console.Write(count + ``" "``);``        ``}``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main(``string``[] args)``    ``{``        ``string` `S = ``"abcdefdefabc"``;``        ``string` `X = ``"abc"``;``        ``string` `Y = ``"def"``;``        ``countOccurrences(S, X, Y);``    ``}``}` `// This code is contributed by ukasp.`

## Javascript

 ``
Output:
`0 2`

Time Complexity: O(N*(A + B))
Auxiliary Space: O(1)

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