我只是不想遍历比较那个个字符串数组而已，内存占用可能比较多，不过我相信时间绝对比遍历比较字符串数组要短，CPU占用也少。

不好Free，所以就不手动Free了……

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

struct balloon_index {
    struct balloon_index *a;
    struct balloon_index *b;
    struct balloon_index *c;
    struct balloon_index *d;
    struct balloon_index *e;
    struct balloon_index *f;
    struct balloon_index *g;
    struct balloon_index *h;
    struct balloon_index *i;
    struct balloon_index *j;
    struct balloon_index *k;
    struct balloon_index *l;
    struct balloon_index *m;
    struct balloon_index *n;
    struct balloon_index *o;
    struct balloon_index *p;
    struct balloon_index *q;
    struct balloon_index *r;
    struct balloon_index *s;
    struct balloon_index *t;
    struct balloon_index *u;
    struct balloon_index *v;
    struct balloon_index *w;
    struct balloon_index *x;
    struct balloon_index *y;
    struct balloon_index *z;
    int count;
};

struct balloon_index *struct_inital();

int main() {
    struct balloon_index *start, *pointer1, **pointer2;
    int amount, i, ii, len, max_count;
    char color[16], max[16];
    while (1) {
        scanf("%d", &amount);
        if (amount == 0)
            break;
        start = struct_inital();
        max_count = 0;
        for (i = 1; i <= amount; i++) {
            scanf("%s", color);
            pointer1 = start;
            len = strlen(color);
            for (ii = 0; ii <= len; ii++) {
                switch (color[ii]) {
                    case 'a':
                        pointer2 = &pointer1->a;
                        pointer1 = pointer1->a;
                        break;
                    case 'b':
                        pointer2 = &pointer1->b;
                        pointer1 = pointer1->b;
                        break;
                    case 'c':
                        pointer2 = &pointer1->c;
                        pointer1 = pointer1->c;
                        break;
                    case 'd':
                        pointer2 = &pointer1->d;
                        pointer1 = pointer1->d;
                        break;
                    case 'e':
                        pointer2 = &pointer1->e;
                        pointer1 = pointer1->e;
                        break;
                    case 'f':
                        pointer2 = &pointer1->f;
                        pointer1 = pointer1->f;
                        break;
                    case 'g':
                        pointer2 = &pointer1->g;
                        pointer1 = pointer1->g;
                        break;
                    case 'h':
                        pointer2 = &pointer1->h;
                        pointer1 = pointer1->h;
                        break;
                    case 'i':
                        pointer2 = &pointer1->i;
                        pointer1 = pointer1->i;
                        break;
                    case 'j':
                        pointer2 = &pointer1->j;
                        pointer1 = pointer1->j;
                        break;
                    case 'k':
                        pointer2 = &pointer1->k;
                        pointer1 = pointer1->k;
                        break;
                    case 'l':
                        pointer2 = &pointer1->l;
                        pointer1 = pointer1->l;
                        break;
                    case 'm':
                        pointer2 = &pointer1->m;
                        pointer1 = pointer1->m;
                        break;
                    case 'n':
                        pointer2 = &pointer1->n;
                        pointer1 = pointer1->n;
                        break;
                    case 'o':
                        pointer2 = &pointer1->o;
                        pointer1 = pointer1->o;
                        break;
                    case 'p':
                        pointer2 = &pointer1->p;
                        pointer1 = pointer1->p;
                        break;
                    case 'q':
                        pointer2 = &pointer1->q;
                        pointer1 = pointer1->q;
                        break;
                    case 'r':
                        pointer2 = &pointer1->r;
                        pointer1 = pointer1->r;
                        break;
                    case 's':
                        pointer2 = &pointer1->s;
                        pointer1 = pointer1->s;
                        break;
                    case 't':
                        pointer2 = &pointer1->t;
                        pointer1 = pointer1->t;
                        break;
                    case 'u':
                        pointer2 = &pointer1->u;
                        pointer1 = pointer1->u;
                        break;
                    case 'v':
                        pointer2 = &pointer1->v;
                        pointer1 = pointer1->v;
                        break;
                    case 'w':
                        pointer2 = &pointer1->w;
                        pointer1 = pointer1->w;
                        break;
                    case 'x':
                        pointer2 = &pointer1->x;
                        pointer1 = pointer1->x;
                        break;
                    case 'y':
                        pointer2 = &pointer1->y;
                        pointer1 = pointer1->y;
                        break;
                    case 'z':
                        pointer2 = &pointer1->z;
                        pointer1 = pointer1->z;
                        break;
                    case '\0':
                        pointer1->count++;
                        if (pointer1->count >= max_count) {
                            max_count = pointer1->count;
                            strcpy(max, color);
                        }
                }
                if (pointer1 == NULL) {
                    *pointer2 = struct_inital();
                    pointer1 = *pointer2;
                }
            }
        }
        printf("%s\n", max);
    }
    return 0;
}

struct balloon_index *struct_inital() {
    struct balloon_index *index;
    index = (struct balloon_index *) malloc(sizeof(struct balloon_index));
    index->a = index->b = index->c = index->d = index->e = index->f = index->g = index->h = index->i = index->j = index->k = index->l = index->m = index->n = index->o = index->p = index->q = index->r = index->s = index->t = index->u = index->v = index->w = index->x = index->y = index->z = NULL;
    index->count = 0;
    return index;
}