两个C语言编程该怎么写？

第一题：

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

#define BUF_SIZE 20

int main()
{
    char a[BUF_SIZE];
    char b[BUF_SIZE];
    char c[BUF_SIZE*2];
    memset(a,0x0,BUF_SIZE);
    memset(b,0x0,BUF_SIZE);
    memset(c,0x0,BUF_SIZE*2);
    char t;
    int i = 0;
    while ((t=getchar()) != '\n')
        a[i++] = t;
    i = 0;
    while ((t=getchar()) != '\n')
        b[i++] = t;
    int k;
    int a_l = strlen(a);
    for(k=0;k<a_l;k++)
        c[k] = a[k];
    int b_l = strlen(b);
    int n = b_l;
    for(i=0;i<b_l;i++)
        c[k+i] = b[--n];
    printf("c=%s\n",c);

    return 0;
}

第二题：

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

int main()
{
    char a[5][20] = {};
    int max_leng = 0;
    int i = 0;
    while (i<5) {
        char t;
        int j = 0;
        while ((t=getchar()) != '\n')
            a[i][j++] = t;
        if(j > max_leng)
            max_leng = j;
        i++;
    }
    for(i=0;i<5;i++)
    {
        int l = strlen(a[i]);
        int k = 0;
        int n = 0;
        while (k<max_leng) {
            if(k < (max_leng-l))
                printf("*");
            else
                printf("%c",a[i][n++]);
            k++;
        }
        printf("\n");
    }
    return 0;
}