Program to print last N lines | Set-2

Given some text lines in one string, each line is separated by ‘\n’ character. Print the last N lines. If the number of lines is less than N, then print all lines.

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

An approach for this problem has been already discussed in Set-1 where only 10 lines were printed. In this post, another approach is discussed for printing the last N lines.

Algorithm:

• Split the string around ‘\n’ using strtok.
• Store the individual strings in a vector.
• Print the last N strings from vector.

Below is the implementation of the above approach:

C++

 `// C++ program to print the last N lines ` `#include ` `using` `namespace` `std; ` ` `  `void` `PrintLast(string s, ``int` `t) ` `{ ` `    ``// Vector to store individual strings. ` `    ``vector v; ` ` `  `    ``// Get a pointer to string. ` `    ``char``* str = &s[0]; ` `    ``// Split the string around '\n'. ` `    ``char``* token = ``strtok``(str, ``"\n"``); ` ` `  `    ``// Save all strings in the vector. ` `    ``while` `(token) { ` `        ``v.push_back(token); ` `        ``token = ``strtok``(NULL, ``"\n"``); ` `    ``} ` ` `  `    ``if` `(v.empty()) { ` `        ``cout << ``"ERROR: string doesn't contain '\\n' character\n"``; ` `        ``return``; ` `    ``} ` ` `  `    ``// If the string has t lines ` `    ``if` `(v.size() >= t) { ` `        ``for` `(``int` `i = v.size() - t; i < v.size(); i++) ` `            ``cout << v[i] << endl; ` `    ``} ` `    ``else` `{ ` `        ``for` `(``int` `i = 0; i < v.size(); i++) ` `            ``cout << v[i] << endl; ` `    ``} ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``string s1 = ``"str1\nstr2\nstr3\nstr4\nstr5\nstr6\nstr7\nstr8\nstr9"` `                ``"\nstr10\nstr11\nstr12\nstr13\nstr14\nstr15\nstr16\nstr17"` `                ``"\nstr18\nstr19\nstr20\nstr21\nstr22\nstr23\nstr24\nstr25"``; ` `    ``int` `n = 10; ` `    ``PrintLast(s1, n); ` ` `  `    ``return` `0; ` `} `

Java

 `// Java program to print the last N lines ` `import` `java.util.*; ` ` `  `class` `GFG  ` `{ ` `    ``static` `void` `printLast(String s, ``int` `t) ` `    ``{ ` ` `  `        ``// Vector to store individual strings. ` `        ``// Save all strings in the vector. ` `        ``String[] v = s.split(``"\n"``); ` ` `  `        ``if` `(v.length == ``0``)  ` `        ``{ ` `            ``System.out.println(``"ERROR: string doesn't "` `+  ` `                              ``"contain '\\n' character"``); ` `            ``return``; ` `        ``} ` ` `  `        ``// If the string has t lines ` `        ``if` `(v.length >= t)  ` `        ``{ ` `            ``for` `(``int` `i = v.length - t; i < v.length; i++) ` `            ``{ ` `                ``System.out.println(v[i]); ` `            ``} ` `        ``}  ` `        ``else`  `        ``{ ` `            ``for` `(``int` `i = ``0``; i < v.length; i++) ` `            ``{ ` `                ``System.out.println(v[i]); ` `            ``} ` `        ``} ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `        ``String s1 = ``"str1\nstr2\nstr3\nstr4\nstr5\nstr6\nstr7"` `+  ` `                    ``"\nstr8\nstr9\nstr10\nstr11\nstr12\nstr13"` `+  ` `                    ``"\nstr14\nstr15\nstr16\nstr17\nstr18\nstr19"` `+  ` `                    ``"\nstr20\nstr21\nstr22\nstr23\nstr24\nstr25"``; ` `        ``int` `n = ``10``; ` `        ``printLast(s1, n); ` `    ``} ` `} ` ` `  `// This code is contributed by ` `// sanjeev2552 `

Python3

 `# Python3 program to print the last N lines  ` `def` `PrintLast(s, t):  ` ` `  `    ``# Vector to store individual strings.  ` `    ``v ``=` `s.split(``'\n'``) ` `     `  `    ``if` `len``(v) ``=``=` `0``:  ` `        ``print``(``"ERROR: string doesn't "``, ` `              ``"contain '\\n' character\n"``)  ` `        ``return` `     `  `    ``# If the string has t lines  ` `    ``elif` `len``(v) >``=` `t:  ` `        ``for` `i ``in` `range``(``len``(v) ``-` `t, ``len``(v)):  ` `            ``print``(v[i])  ` `     `  `    ``else``: ` `        ``for` `i ``in` `range``(``0``, ``len``(v)):  ` `            ``print``(v[i]) ` `     `  `# Driver Code  ` `if` `__name__ ``=``=` `"__main__"``: ` ` `  `    ``s1 ``=` `"str1\nstr2\nstr3\nstr4\nstr5\nstr6"` `+` `\ ` `         ``"\nstr7\nstr8\nstr9\nstr10\nstr11"` `+` `\ ` `         ``"\nstr12\nstr13\nstr14\nstr15\nstr16"` `+` `\ ` `         ``"\nstr17\nstr18\nstr19\nstr20\nstr21"` `+` `\ ` `         ``"\nstr22\nstr23\nstr24\nstr25"` `     `  `    ``n ``=` `10` `    ``PrintLast(s1, n)  ` ` `  `# This code is contributed by Rituraj Jain `

Output:

```str16
str17
str18
str19
str20
str21
str22
str23
str24
str25
```

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Improved By : rituraj_jain, sanjeev2552

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