C：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct node
{
    char data[30];
    struct node *lc;
    struct node *rc;
    int num;
};
char a[30];
int n;
struct node *creat(struct node *root)
{
    if(root == NULL)
    {
        root = (struct node *)malloc(sizeof(struct node));
        root->lc = NULL;
        root->rc = NULL;
        root->num = 1;
        strcpy(root->data, a);
    }
    else
    {
        if(strcmp(a, root->data) == 0)
        {
            root->num++;
        }
        else if(strcmp(a, root->data) < 0)
        {
            root->lc = creat(root->lc);
        }
        else
        {
            root->rc = creat(root->rc);
        }
    }
    return root;
};
void fin(struct node *root)
{
    if(root != NULL)
    {
        fin(root->lc);
        printf("%s %.2lf%%\n", root->data, 1.0 * root->num * 100 / n);
        fin(root->rc);
    }
}
int main()
{
    int i, j;
    int len;
    struct node *root;
    scanf("%d ", &n);
    root = NULL;
    for(i = 0; i < n; i++)
    {
        gets(a);
        len = strlen(a);
        for(j = 0; j < len; j++)
        {
            if(a[j] >= 'A' && a[j] <= 'Z')
            {
                a[j] = a[j] + 32;
            }
        }
        root = creat(root);
    }
    fin(root);
    return 0;
}