reverse.c

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

struct substring
{
  char *inner;
	int  lower, upper;
};

void
set_value(struct substring *s, char *v)
{
	s->inner = v;
	s->lower = 0;
	s->upper = strlen(v);
}

int
_find_space(struct substring s)
{
	int i;
	for(i = s.upper - 1; i >= s.lower; --i) {
		if(s.inner[i] == ' ') {
			return i;
		}
	}
	return -1;
}

// This function assumes str has space to acommodate s.
void
subconcat(struct substring s, char *str)
{
	int i, j = strlen(str);
	for(i = s.lower; i < s.upper; ++i, ++j) {
		str[j] = s.inner[i];
	}
	if(s.lower > 0 && s.inner[s.lower - 1] == ' ') {
		str[j++] = ' ';
	}
	str[j] = '\0';
}

int
reverse(int n, char **input, char **output)
{
	int i, index;
	struct substring s;
	for(i = 0; i < n; ++i) {
		output[i][0] = '\0';
	}
	for(i = 0; i < n; ++i) {
		index = -1;
		set_value(&s, input[i]);
		do {
			if(index >= 0) {
				s.upper = index;
			}
			index = _find_space(s);
			s.lower = index + 1;
			subconcat(s, output[i]);
			s.lower = 0;
		} while(index >= 0);
	}
	return 0;
}

void
readline(char *str)
{
	char c;
	int i;
	for(i = 0; (c = getchar()) != EOF && c != '\n'; ++i) {
		str[i] = c;
	}
	str[i] = '\0';
}

int
main(void)
{
	int i, n;
	char **words, **output;
	scanf("%d\n", &n);
	words = (char **)malloc(n * sizeof(char *));
	output = (char **)malloc(n * sizeof(char *));
	for(i = 0; i < n; ++i) {
		words[i] = (char *)malloc(n * n *sizeof(char));
		readline(words[i]);
		output[i] = (char *)malloc(n * n *sizeof(char));
	}
	reverse(n, words, output);
	for(i = 0; i < n; ++i) {
		printf("Case #%d: %s\n", i+1, output[i]);
	}
	return 0;
}