{"post":"

The small parts of a string, are known as substrings. These substrings can be of any length, but, they need to be in order. We cannot skip any letters in between while choosing the substrings.

For example:

Sun={s,u,n,su,un,sun} are substrings.
\nwhile, {sn,ns,nu,us,nus,uns} cannot be called as substring of it.

There are two ways to do this:

When the starting index and length of substring is given.
When the starting index and length of substring is not given.

In the first approach, We have two methods

Using a user-defined function.
Without using function.

In the second approach, we have one method

Print all substrings.

Method 1: Using user-defined function, when starting index and length is given

Logic:

In this method, we take the starting index of substring and length from user. We pass these values in the function. In the function, using loop, we copy the characters from str to substr string, till the length inputted by user.

Algorithm:

Take string input in str
Store length of string in len
Next, get the starting index from user as, start
Get starting indes from user as endlen
Call the functions after checking the necessary constraints
In the function, take a for loop from start to endlen
Initialize another string as substr, copy characters of str in substr.
Print substr.

Code:
\n

#include <iostream>\r\n#include <string>\r\nusing namespace std;\r\nvoid substring(string str, int start, int length)\r\n{\r\n\tint i=start, j;\r\n\tstring substr;\r\n\tfor(j = 0; str[i] !='\\0' && length > 0; i++, j ++)\r\n\t\t{\r\n\t\t\tsubstr[j] = str[i];\r\n\t\t\tlength--;\r\n\t\t}\r\n\tsubstr[j] = '\\0';        \r\ncout<<\"\\n\";\r\n\tfor(int k=0;substr[k]!='\\0';k++) \r\n\t    cout<<substr[k];\r\n}\r\nint main()\r\n{\r\n\tstring str;\r\n\tint start,endlen,len;\r\n\tcout<<\"Enter a string: \";\r\n\tgetline(cin,str);\r\n\tlen=str.length();\r\n\tcout<<\"\\n Enter starting position of substring : \";\r\n\tcin>>start ;\r\n\tcout<<\"\\n Enter length of substring: \" ;\r\n\tcin>>endlen;\r\n\tif(start > 0 && start < 30 && endlen<len )\r\n\t\tsubstring(str,start,endlen);\r\n\telse\r\n\t\tcout<<\"Values are invalid\\n\";\r\n\treturn 0;\r\n}

Output:

Enter a string: GoodMorning\r\nEnter starting position of substring :4\r\nEnter length of substring: 7\n

Morning

Method 2: Without Using user-defined function, when starting index and length is given

Logic:

this method, is similar to what previously we saw. The difference is that we do not use function here.

Algorithm:

Take string input in str
Store length of string in len
Next, get the starting index from user as, start
Get starting indes from user as endlen
Check the necessary constraints
If values are bounded by the constraints, take a for loop from start to endlen
Initialize another string as substr, copy characters of str in substr.
Print substr.

Code:
\n

#include <iostream>\r\n#include <string>\r\nusing namespace std;\r\nint main()\r\n{\r\n\tstring str,substr;\r\n\tint start,endlen,len;\r\n\tcout<<\"Enter a string: \";\r\n\tgetline(cin,str);\r\n\tlen=str.length();\r\n\tcout<<\"\\n Enter starting position of substring : \";\r\n\tcin>>start ;\r\n\tcout<<\"\\n Enter length of substring: \" ;\r\n\tcin>>endlen;\r\n\tif(start > 0 && start < 30 && endlen<len )\r\n\t{\r\n\t\tint i=start,stopping_position;\r\n\t\t cout<<\"\\n\";\r\n\t\tfor(int j = 0; i<len && endlen > 0; i++, j ++)\r\n\t\t{\r\n\t\t\tsubstr[j] = str[i];\r\n\t\t\tendlen--;\r\n\t\t\tstopping_position=j;\r\n\t\t}\r\n\t\tsubstr[stopping_position+1] = '\\0';           \n    for(int k=0;substr[k]!='\\0';k++)\r\n        cout&lt;&lt;substr[k];\r\n}\r\nelse\r\n\tcout&lt;&lt;\"Values are invalid\\n\";\r\nreturn 0;\n
\n}

Output:

Enter a string: TomandJerry\r\nEnter starting position of substring : 6\r\nEnter length of substring: 5\r\nJerry

Method 3: Print all substrings

Logic:

In this method, we print all the possible substrings. We take length 1, and print all substrings with length 1, then we take 2 and print all the substrings with length 2. In this way, we progress, till we reach the length of the substrings.

Algorithm:

Take string input
Store its length
Run a for loop till the end of string, to get the starting point of a substring
Nest another loop inside it, which keeps the ending point of a substring
Now, nest third loop to it, such that, we print all the characters determined by the starting and ending point.

Code:
\n

#include <iostream>\r\n#include <string>\r\nusing namespace std;\r\nint main()\r\n{\r\n\tstring str;\r\n\tint len;\r\n\tcout<<\"Enter a string: \";\r\n\tgetline(cin,str);\r\n\tlen=str.length();\nfor(int i=1; i&lt;=len; i++)\r\n{\r\n\tfor (int j = 0; j &lt;= (len-i); j++)\r\n\t{\r\n    \tcout&lt;&lt;\"\\n\";\t\r\n    \tfor (int k = j; k &lt;= i+j-1; k++)\r\n    \t\tcout&lt;&lt;str[k];\r\n\t}\r\n}\n
\nreturn 0;\r\n}

Output:

Enter a string: Help\r\nH\r\ne\r\nl\r\np\r\nHe\r\nel\r\nlp\r\nHel\r\nelp\r\nHelp

\n","title":"substring function in C++ | Extract Substring Program C++","authorDetails":{"name":"Juhi Kamdar","slug":"juhi-kamdar"},"seo":{"title":"substring function in C++ | Extract Substring Program C++"},"description":"Learn to extract substring from a given string in C++ programming using substr function in C++ and without using function. We'll learn three different methods to extract substring.","slug":"cpp/examples/program-to-extract-substrings-from-a-given-string-in-cpp/","articleId":"636a83457bb1ce5072622bfa","bookmarkStatus":{"isBookmarked":false,"bookmarkId":null}}