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Program to print last N lines in c++
In this tutorial, we will be discussing a program to print the last N lines.
For this, we will be provided with a string that consists of the new line character to denote the start of the next line and the number of lines to be printed from the last. Our task is to start from the last and print all the N lines counting from the last.
Example
#include <bits/stdc++.h>
using namespace std;
#define DELIM '\n'
//printing the last N lines
void print_last_lines(char *str, int n){
if (n <= 0)
return;
size_t cnt = 0; //storing the number of lines
char *target_pos = NULL;
//finding the initial position of last line
target_pos = strrchr(str, DELIM);
if (target_pos == NULL){
cout << "Given string is a single line string";
return;
}
//moving to the start position of the 1st line
while (cnt < n){
//moving to the next lines
while (str < target_pos && *target_pos != DELIM)
--target_pos;
if (*target_pos == DELIM)
--target_pos, ++cnt;
//if string has less than 10 lines the break
else
break;
}
if (str < target_pos)
target_pos += 2;
cout << target_pos << endl;
}
int main(void){
char *str1 ="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";
print_last_lines(str1, 14);
return 0;
}Output
str12 str13 str14 str15 str16 str17 str18 str19 str20 str21 str22 str23 str24 str25
Updated on: 02-Jan-2020
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