Ans1

****
4-1
****

#define NULL ((void*)0)
#include <stdio.h>

struct leaf {
    char data[16]; /* string data */
    struct leaf *next; /* pointer to the next leaf */
};

struct leaf *addLeaf(char*, struct leaf *);
struct leaf *insertLeaf(char*, struct leaf *, int);
void printLeaves(struct leaf *p);
void freeLeaves(struct leaf *p);
int main(void)
{
    int pos;
    char name[16];
    printf ("Please insert new element's name: \n");
    scanf("%s", &name);
    printf ("Please insert new element's position: \n");
    scanf("%d", &pos);
    struct leaf *top; /* top of the leaves */
    char *fruits[4] = {"apple", "orange", "banana", name} ;
    top = NULL;
    top = addLeaf(fruits[0], top);
    top = addLeaf(fruits[1], top);
    top = addLeaf(fruits[2], top);
    insertLeaf(fruits[3], top, pos);
    printLeaves(top); /* print elements*/
    freeLeaves(top); /* delete all elements */
}

void printLeaves(struct leaf *pL)
{
    while (pL != NULL) {
        printf("%s\n", pL->data);
        pL = pL->next;
    }
}

struct leaf *addLeaf(char *data, struct leaf *top)
{
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    /* change pointer to the top */
    pL->next = top; /* Old top is new leaf's next */
    top = pL;/* New top is new leaf's address */
    return top;
}

struct leaf *insertLeaf(char *data, struct leaf *top, int pos)
{
    int count = 0;
    struct leaf *pTail;
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    if (pos == 0)
    {
        /* change pointer to the top */
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
    else
    {
        while (count != pos)
        {
            pTail  = top;
            top = top->next;
            count++;
        }
        /*change pointer to the top */
        pTail->next = pL;
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
}

void freeLeaves(struct leaf *pL)
{
    struct leaf *pLnext;
    while (pL != NULL) {
        pLnext = pL->next;
        free(pL);
        pL = pLnext;
    }
}

*****
4-2-1
*****

#define NULL ((void*)0)
#include <stdio.h>

struct leaf {
    char data[16]; /* string data */
    struct leaf *next; /* pointer to the next leaf */
};

struct leaf *addLeaf(char*, struct leaf *);
struct leaf *insertLeaf(char*, struct leaf *, int);
struct leaf *removeLeaf(struct leaf *);
void printLeaves(struct leaf *p);
void freeLeaves(struct leaf *p);
int main(void)
{
    int pos;
    char name[16];
    //printf ("Please insert new element's name: \n");
    //scanf("%s", &name);
    //printf ("Please insert new element's position: \n");
    //scanf("%d", &pos);
    struct leaf *top; /* top of the leaves */
    char *fruits[4] = {"apple", "orange", "banana", "grape"} ;
    top = NULL;
    top = addLeaf(fruits[0], top);
    top = addLeaf(fruits[1], top);
    top = addLeaf(fruits[2], top);
    top = addLeaf(fruits[3], top);
    //insertLeaf(fruits[3], top, pos);
    removeLeaf (top);
    printLeaves(top); /* print elements*/
    freeLeaves(top); /* delete all elements */
}

void printLeaves(struct leaf *pL)
{
    while (pL != NULL) {
        printf("%s\n", pL->data);
        pL = pL->next;
    }
}

struct leaf *addLeaf(char *data, struct leaf *top)
{
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    /* change pointer to the top */
    pL->next = top; /* Old top is new leaf's next */
    top = pL;/* New top is new leaf's address */
    return top;
}

struct leaf *insertLeaf(char *data, struct leaf *top, int pos)
{
    int count = 0;
    struct leaf *pTail;
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    if (pos == 0)
    {
        /* change pointer to the top */
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
    else
    {
        while (count != pos)
        {
            pTail  = top;
            top = top->next;
            count++;
        }
        /*change pointer to the top */
        pTail->next = pL;
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
}

struct leaf *removeLeaf(struct leaf *top)
{
    struct leaf *pL;
    pL = top->next;
    top->next = top->next->next;
    free(pL);
}

void freeLeaves(struct leaf *pL)
{
    struct leaf *pLnext;
    while (pL != NULL) {
        pLnext = pL->next;
        free(pL);
        pL = pLnext;
    }
}

*********
4-2-2
*********

#define NULL ((void*)0)
#include <stdio.h>

struct leaf {
    char data[16]; /* string data */
    struct leaf *next; /* pointer to the next leaf */
};

struct leaf *addLeaf(char*, struct leaf *);
struct leaf *insertLeaf(char*, struct leaf *, int);
struct leaf *removeLeaf(struct leaf *, int);
void printLeaves(struct leaf *p);
void freeLeaves(struct leaf *p);
int main(void)
{
    int pos;
    char name[16];
    int rpos;
    printf ("Please insert position to remove: \n");
    scanf("%d", &rpos);
    //printf ("Please insert new element's name: \n");
    //scanf("%s", &name);
    //printf ("Please insert new element's position: \n");
    //scanf("%d", &pos);
    struct leaf *top; /* top of the leaves */
    char *fruits[4] = {"apple", "orange", "banana", "grape"} ;
    top = NULL;
    top = addLeaf(fruits[0], top);
    top = addLeaf(fruits[1], top);
    top = addLeaf(fruits[2], top);
    top = addLeaf(fruits[3], top);
    //insertLeaf(fruits[3], top, pos);
    removeLeaf (top, rpos);
    printLeaves(top); /* print elements*/
    freeLeaves(top); /* delete all elements */
}

void printLeaves(struct leaf *pL)
{
    while (pL != NULL) {
        printf("%s\n", pL->data);
        pL = pL->next;
    }
}

struct leaf *addLeaf(char *data, struct leaf *top)
{
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    /* change pointer to the top */
    pL->next = top; /* Old top is new leaf's next */
    top = pL;/* New top is new leaf's address */
    return top;
}

struct leaf *insertLeaf(char *data, struct leaf *top, int pos)
{
    int count = 0;
    struct leaf *pTail;
    struct leaf *pL;
    pL = (struct leaf*) malloc(sizeof(struct leaf));
    strcpy(pL->data, data);
    if (pos == 0)
    {
        /* change pointer to the top */
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
    else
    {
        while (count != pos)
        {
            pTail  = top;
            top = top->next;
            count++;
        }
        /*change pointer to the top */
        pTail->next = pL;
        pL->next = top; /* Old top is new leaf's next */
        top = pL; /* New top is new leaf's address */
    }
}

struct leaf *removeLeaf(struct leaf *top, int rpos)
{
    struct leaf *pL;
    int count = 0;
    if (rpos == 0)
    {
        pL = top->next;
        free(top);
        top = pL;
        return top;
    }
    else
    {
        while (count < rpos-1)
        {
        top = top->next;
        count ++;
        }
    pL = top->next;
    top->next = top->next->next;
    free(pL);
    }
}

void freeLeaves(struct leaf *pL)
{
    struct leaf *pLnext;
    while (pL != NULL) {
        pLnext = pL->next;
        free(pL);
        pL = pLnext;
    }
}

**********
6
********

#define NULL ((void*)0)
#include <stdio.h>
#include <stdlib.h>

void *create(int*);
void show(int*);
int main()
{
    int a[10];
    show(create(a));
    return(0);
}
void *create(int *a)
{
    int i;
    srand (time(NULL));
    for (i=0;i<10;i++)
    {
        a[i] = rand() % 10;
    }
    return a;
}

void show(int *a)
{
    int i;
    for (i=0;i<10;i++)
    {
        printf ("%d\n", a[i]);
    }
}

**********
Gue
*********

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <conio.h>
#define NUMLEN 4
int isMatch(char*, char*);
int isValidNumber(char*);
char *createRandomNumber(char*);

int main(void)
{
    int i = 0;
    int a = 0;
    char num[NUMLEN];
    char target[NUMLEN];
    unsigned r;
    printf ("Please insert a seed to generate random numbers: ", r);
    scanf ("%u", &r);
    srand (time(NULL));
    while (i == 0)
    {
        i = isValidNumber(createRandomNumber(target));
    }
    printf ("Psst! The number is: ");
    for (i = 0;i < NUMLEN; i++)
    {
        printf ("%d", target[i]);
    }
    printf ("\n");
    while (a == 0)
    {
        //for(i = 0; i < NUMLEN; i++)
        //{
            printf("Enter a Number: ");
            scanf("%s", num);
        //}
        for(i = 0; i < NUMLEN; i++)
        {
            num[i] -= 48;
        }
        a = isValidNumber(num);
        if (a == 0)
        {
            printf("Invalid inputs! Duplicate numbers. Please try again \n");
        }
    }

    for (i = 0; i < NUMLEN; i++)
    {
        printf ("%d", num[i]);
    }

    a = isMatch(target, num);
    if (1 == a)
    {
        printf ("\nCorrect!");
    }
    else
    {
        printf ("\nIncorrect!");
    }
	getch();
}

char *createRandomNumber(char *target)
{
    int i;
    for (i = 0;i < 4; i++)
    {
        target[i] = rand() % 10;
    }
    return target;
}

int isValidNumber(char *target)
{
    int i;
    int j;
    for (i = 0; i < 4; i++)
    {
        for (j = i + 1; j < 4; j++)
        {
            if (target[i] == target[j])
            {
                return 0;
            }
        }
    }
    return 1;
}

int isMatch(char *target, char *num)
{
    int i;
    int j;
    int hit = 0;
    int blow = 0;
    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < 4; j++)
        {
            if (j == i && target[i] == num[j])
            {
                hit++;
            }
            else if (j != i && target[i] == num[j])
            {
                blow++;
            }
            else
            {
                continue;
            }
        }
    }
	printf ("\nHit count: %d\n", hit);
	printf ("\nBlow count: %d\n", blow);
	if (4 == hit)
	{
		return 1;
	}
	else
	{
		return 0;
	}
}