Task: Word wrap

C: #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>


const char *string = "In olden times when wishing still helped one, there lived a king "
    "whose daughters were all beautiful, but the youngest was so beautiful "
    "that the sun itself, which has seen so much, was astonished whenever "
    "it shone-in-her-face.  Close-by-the-king's castle lay a great dark "
    "forest, and under an old lime-tree in the forest was a well, and when "
    "the day was very warm, the king's child went out into the forest and "
    "sat down by the side of the cool-fountain, and when she was bored she "
    "took a golden ball, and threw it up on high and caught it, and this "
    "ball was her favorite plaything.";



#define PENALTY_LONG    100
#define PENALTY_SHORT   1

typedef struct word_t {
    const char *s;
    int len;
} *word;

word make_word_list(const char *s, int *n)
{
    int max_n = 0;
    word words = 0;

    *n = 0;
    while (1) {
        while (*s && isspace(*s)) s++;
        if (!*s) break;

        if (*n >= max_n) {
            if (!(max_n *= 2)) max_n = 2;
            words = realloc(words, max_n * sizeof(*words));
        }
        words[*n].s = s;
        while (*s && !isspace(*s)) s++;
        words[*n].len = s - words[*n].s;
        (*n) ++;
    }

    return words;
}

int greedy_wrap(word words, int count, int cols, int *breaks)
{
    int score = 0, line, i, j, d;

    i = j = line = 0;
    while (1) {
        if (i == count) {
            breaks[j++] = i;
            break;
        }

        if (!line) {
            line = words[i++].len;
            continue;
        }

        if (line + words[i].len < cols) {
            line += words[i++].len + 1;
            continue;
        }

        breaks[j++] = i;
        if (i < count) {
            d = cols - line;
            if (d > 0)  score += PENALTY_SHORT * d * d;
            else if (d < 0) score += PENALTY_LONG * d * d;
        }

        line = 0;
    }
    breaks[j++] = 0;

    return score;
}


int balanced_wrap(word words, int count, int cols, int *breaks)
{
    int *best = malloc(sizeof(int) * (count + 1));

    
    int best_score = greedy_wrap(words, count, cols, breaks);

    void test_wrap(int line_no, int start, int score) {
        int line = 0, current_score = -1, d;

        while (start <= count) {
            if (line) line ++;
            line += words[start++].len;
            d = cols - line;
            if (start < count || d < 0) {
                if (d > 0)
                    current_score = score + PENALTY_SHORT * d * d;
                else
                    current_score = score + PENALTY_LONG * d * d;
            } else {
                current_score = score;
            }

            if (current_score >= best_score) {
                if (d <= 0) return;
                continue;
            }

            best[line_no] = start;
            test_wrap(line_no + 1, start, current_score);
        }
        if (current_score >= 0 && current_score < best_score) {
            best_score = current_score;
            memcpy(breaks, best, sizeof(int) * (line_no));
        }
    }
    test_wrap(0, 0, 0);
    free(best);

    return best_score;
}

void show_wrap(word list, int count, int *breaks)
{
    int i, j;
    for (i = j = 0; i < count && breaks[i]; i++) {
        while (j < breaks[i]) {
            printf("%.*s", list[j].len, list[j].s);
            if (j < breaks[i] - 1)
                putchar(' ');
            j++;
        }
        if (breaks[i]) putchar('\n');
    }
}

int main(void)
{
    int len, score, cols;
    word list = make_word_list(string, &len);
    int *breaks = malloc(sizeof(int) * (len + 1));

    cols = 80;
    score = greedy_wrap(list, len, cols, breaks);
    printf("\n== greedy wrap at %d (score %d) ==\n\n", cols, score);
    show_wrap(list, len, breaks);

    score = balanced_wrap(list, len, cols, breaks);
    printf("\n== balanced wrap at %d (score %d) ==\n\n", cols, score);
    show_wrap(list, len, breaks);


    cols = 32;
    score = greedy_wrap(list, len, cols, breaks);
    printf("\n== greedy wrap at %d (score %d) ==\n\n", cols, score);
    show_wrap(list, len, breaks);

    score = balanced_wrap(list, len, cols, breaks);
    printf("\n== balanced wrap at %d (score %d) ==\n\n", cols, score);
    show_wrap(list, len, breaks);

    return 0;
}











Ada: generic
   with procedure Put_Line(Line: String);
package Word_Wrap is

   type Basic(Length_Of_Output_Line: Positive) is tagged private;

   procedure Push_Word(State: in out Basic; Word: String);
   procedure New_Paragraph(State: in out Basic);
   procedure Finish(State: in out Basic);

private
   type Basic(Length_Of_Output_Line: Positive) is tagged record
      Line: String(1 .. Length_Of_Output_Line);
      Size: Natural := 0; 
      Top_Of_Paragraph: Boolean := True;
   end record;

end Word_Wrap;