#include <stdio.h>
#include <stdlib.h>
enum {NAME_LEN_MAX=100,GROUP_NAME_MAX=20};

typedef struct {
	char name[NAME_LEN_MAX];
	char group[GROUP_NAME_MAX];
	int sex;
	int height;
} student;

void fill_student(student * stud);

int main(int argc, char ** argv){
	int stud_count = 0;
	(void)printf("Enter the count of students: ");
	(void)scanf("%d",&stud_count);
	student * students = malloc(stud_count * sizeof(student));
	
	for(int i=0; i < stud_count; i++)
		fill_student(&students[i]);
	for(int i=0; i < stud_count - 1; i++) 
		for(int j=i+1; j < stud_count; j++)
			if(students[i].height == students[j].height) 
				(void)printf("They have equivalent height(%d) %s and %s\n",
				students[i].height,students[i].name,students[j].name);
	exit(EXIT_SUCCESS);
}

void fill_student(student * stud) {
	printf("Enter the name: ");
	scanf("%s",stud->name);
	printf("Enter the group: ");
	scanf("%s",stud->group);
	printf("Enter the sex [0 or 1]: ");
	scanf("%d",&stud->sex);
	printf("Enter the height: ");
	scanf("%d",&stud->height);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum{STRING_LEN_MAX=250};

int main(int arg,char ** argv) {
	FILE * fd = fopen("infile.txt","r");
	FILE * out_file = fopen("outfile.txt","w");
	
	char buf[STRING_LEN_MAX];
	int i=1;
	int all_count=0;
	
	(void)fgets(buf,STRING_LEN_MAX,fd);
	while(!feof(fd)){
		int cur_string_count=0;
		for(int j=0; j<strlen(buf)-1;j++)
			if(buf[j]=='f'&&(buf[j+1]==' '||buf[j+1]==','||buf[j+1]=='.'))
				++cur_string_count;
		
		if(buf[strlen(buf)-2]=='f') 
			++cur_string_count;
			
		if(cur_string_count>0)
			(void)fprintf(out_file,"String number %d have %d words\n",i,cur_string_count);
			
		all_count+=cur_string_count;
		++i;
		
		(void)fgets(buf,STRING_LEN_MAX,fd);
	}
	
	(void)fprintf(out_file,"Total: %d\n",all_count);
	
	fclose(fd);
	fclose(out_file);
	exit(EXIT_SUCCESS);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum{STRING_COUNT_MAX=100,STRING_LEN_MAX=250};

int main(int argc, char ** argv){
	FILE * infile = fopen("infile.txt","r");
	char * strings[STRING_COUNT_MAX];
	char buf[STRING_LEN_MAX];
	int string_num = 0;
	(void)fgets(buf,STRING_LEN_MAX,infile);
	while(!feof(infile)) {
		strings[string_num]=calloc(STRING_LEN_MAX,sizeof(char));
		for(int i=1,j=0;i<strlen(buf);i++){
			if(buf[i]==' ' && buf[i-1]==' ')
				continue;
			else 
				strings[string_num][j++]=buf[i];
		}
		++string_num;
		(void)fgets(buf,STRING_LEN_MAX,infile);
	}
	fclose(infile);
	infile = fopen("infile.txt","w");
	for(int i=0;i<string_num; i++) 
		(void)fprintf(infile,"%s\n",strings[i]);
	fclose(infile);
	exit(EXIT_SUCCESS);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum{STRING_COUNT_MAX=100,STRING_LEN_MAX=250};

int main(int argc, char ** argv) {
	int last_lines=0, string_num=0;
	if(argc == 2) 
		last_lines = atoi(argv[1]);
	FILE * infile = fopen("infile.txt","r");
	
	char buf[STRING_LEN_MAX];
	char * strings[STRING_COUNT_MAX];
	(void)fgets(buf,STRING_LEN_MAX,infile);
	
	while(!feof(infile)){
		
		strings[string_num] = calloc(STRING_LEN_MAX,sizeof(char));
		(void)strcpy(strings[string_num++],buf);
		(void)fgets(buf,STRING_LEN_MAX,infile);
	}
	
	int string_index = 0;
	if(last_lines != 0)
		string_index = string_num - last_lines;
		
	if(string_index < 0) string_index = 0;
	
	for(int i = string_index; i < string_num; i++)
		(void)printf("%s",strings[i]);
		
	fclose(infile);
	exit(EXIT_SUCCESS);
}