1.c

#include <stdio.h>
#include <windows.h>

int main() {
	//Set windows-1251 codepage
	SetConsoleCP(1251);
	SetConsoleOutputCP(1251);	

	//Memory init
	char * str = new char[100];
	char * res = new char[100];
	char * word_begin = str, *iterator, *iterator_two, *progress = res;
	
	int count = 0;
	
	//Reading
	puts("Ââåäèòå ñòðîêó: ");
	gets(str); //not-safe use fgets
	
	//task
	int length = strlen(str);
	for (int i = 0; i <= length; ++i) {
		iterator = str + i;
		//word break
		if (*iterator == ' ' || *iterator == '\0') {
			//counting
			for (iterator_two = word_begin; iterator_two < iterator; ++iterator_two) {
				if (*iterator_two == *(iterator - 1)) {
					count++;
				}
			}
			
			//adding first symbols
			while (count != 0) {
				*progress = *(iterator - 1);
				progress++;
				count--; 	
			} 
			
			//copying word
			strncpy(progress, word_begin, iterator - word_begin + 1);
			progress += iterator - word_begin + 1;
			
			//move output ptr
			word_begin = iterator + 1;
		}
	}
	puts(res);

	//free mem
	delete [] str;
	delete [] res;	
	return 0;	
}