递归函数进行子串搜索

给定文本txt []和模式pat []，编写一个递归函数“ contains(char pat []，char txt [])”，如果pat []存在于txt []中，则返回true，否则返回false。

例子：

1) Input:   txt[] =  "THIS IS A TEST TEXT"
            pat[] = "TEST"
  Output:  true


2) Input:  txt[] =  "geeksforgeeks"
           pat[] = "quiz"
  Output:  false;

强烈建议您最小化浏览器，然后自己尝试。

下面是递归算法。

contains(tex[], pat[])
    1) If the current character is the last character of the text, but pat
       has more characters, return false.

    2) Else If the current character is the last character of the pattern,
       then return true

    3) Else If current characters of pat and text match, then
        return contains(text + 1, pat + 1);

    4) Else If current characters of pat and text don't match
        return contains(text + 1, pat);

下面是上述算法的实现。

C++

// Recursive C++ program to find if a given pattern is 
// present in a text
#include
using namespace std;
  
bool exactMatch(char *text, char *pat)
{
    if (*text == '\0' && *pat != '\0')
        return false;
  
    // Else If last character of pattern reaches
    if (*pat == '\0')
        return true;
  
    if (*text == *pat)
        return exactMatch(text + 1, pat + 1);
  
    return false;
}
  
// This function returns true if 'text' contain 'pat'
bool contains(char *text, char *pat)
{
    // If last character of text reaches
    if (*text == '\0')
        return false;
  
    // If current characters of pat and text match
    if (*text == *pat)
        if(exactMatch(text, pat))
            return 1;
        else
          return contains(text + 1, pat);
  
    // If current characters of pat and tex don't match
    return contains(text + 1, pat);
}
  
// Driver program to test above function
int main()
{
    cout << contains("geeksforgeeks", "geeks") << endl;
    cout << contains("geeksforgeeks", "geeksquiz") << endl;
    cout << contains("geeksquizgeeks", "quiz") << endl;
    return 0;
}

Python3

# Recursive Python3 program to find if a given pattern is 
# present in a text
  
def exactMatch(text, pat, text_index, pat_index):
    if text_index == len(text) and pat_index != len(pat):
        return 0
   
    # Else If last character of pattern reaches
    if pat_index == len(pat):
        return 1
   
    if text[text_index] == pat[pat_index]:
        return exactMatch(text, pat, text_index+1, pat_index+1)
   
    return 0
  
   
# This function returns true if 'text' contain 'pat'
def contains(text, pat, text_index, pat_index):
    # If last character of text reaches
    if text_index == len(text):
        return 0
   
    # If current characters of pat and text match
    if text[text_index] == pat[pat_index]:
        if exactMatch(text, pat, text_index, pat_index):
            return 1
        else:
            return contains(text, pat, text_index+1, pat_index)
   
    # If current characters of pat and tex don't match
    return contains(text , pat, text_index+1, pat_index)
   
# Driver program to test the above function
  
print(contains("geeksforgeeks", "geeks", 0, 0))
print(contains("geeksforgeeks", "geeksquiz", 0, 0))
print(contains("geeksquizgeeks", "quiz", 0, 0))
  
# This code is contributed by ankush_953.

输出：

1
0
1