SSD 06 Practical Quiz 2人解答

1.
Are there any memory errors in the following program? If so, identify all of the errors and provide a corrected code fragment to alleviate the problem. Assume that the user enters in correct input, and that the sizes entered are at least one. Write your solution in a text or Word file and submit it below.

void main() {
        char *str, *input;
        int *ilist;
        int i, size1, size2;
        
        printf("Number of letters in word: ");
        scanf("%d", &size1);                    /* user inputs an integer */
        printf("Number of integers: ");
        scanf("%d", &size2);                    /* user inputs an integer */
        
        str = (char *) malloc(size1);
        ilist = (int *) malloc(size2);
        
        printf("Word: ");
        scanf("%s", str);                       /* user inputs a string */
        for(i = 0; i < size2; i++) {
                printf("Number %d of %d: ", i + 1, size2);
                scanf("%d", ilist + i);         /* user inputs an integer */
        }
}

2.
Are there any memory errors in the following program? If so, identify all of the errors and provide a corrected code fragment to alleviate the problem. Write your solution in a text or Word file and submit it below.

/* return 1 if str is "1", 0 otherwise */
int checkIf1(char *str) {
        char *newstr = malloc(strlen(str) + 1);
        strcat(newstr, str); /* set newstr to str */
        if (strcmp(newstr, "1") == 0) { /* newstr is "1" */
                return 1;
        }
        free(newstr);
        return 0;
}

void main() {
        char *strArr[4] = {"1", "2", "3", "4"};
        int i;
        
        for(i = 0; i < 4; i++) {
                printf("%d
", checkIf1(strArr[i]));
        }
}

3.
Are there any memory errors in the following program? If so, identify all of the errors and provide a corrected code fragment to alleviate the problem. Write your solution in a text or Word file and submit it below.

struct data {
        char *str1, *str2;
}; 

/* returns two strings concatenated if they are not the same, NULL otherwise */
char *mergeSingleIfDifferent(char *s1, char *s2) {
        char *str = (char *) malloc(strlen(s1) + strlen(s2) + 1);
        if (strcmp(s1, s2) == 0) { /* strings are equal */
                str = NULL;
        }
        else {
                strcpy(str, s1);
                strcat(str, s2);
        }
        return str;
}

/* copies merged strings (or NULL) into array of strings passed in (results) */
void mergeArrayIfDifferent(char *results[], char *strA1[], char *strA2[], int size) {
        int i;
        
        for(i = 0; i < size; i++) {
                results[i] = mergeSingleIfDifferent(strA1[i], strA2[i]);                
        }
}

void printAndFree(int c, char *str) {
        if (str != NULL) {
                printf("%d: %s
", c, str);
                free(str);
        }
}

void main() {
        char *strArr1[8] = {"1", "2", "3", "4", "5", "6", "7", "8"};
        char *strArr2[8] = {"a", "2", "c", "4", "e", "6", "g", "8"};
        char *results[8];
        int i;
        
        mergeArrayIfDifferent(results, strArr1, strArr2, 8);
        for(i = 0; i < 8; i++) {
                printAndFree(i, results);
        }
}