Assignment 7

assignment7.txt

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+Sean Kee
+
+1. For ++*p, it is read right to left. For *p++, it first adds, then does the *p. For *++p, it also reads right to left.
+
+2. Yes, left to right or right to left is guarenteed because the compiler uses a sort of "order of operations" in it's own sense. For terms that are the same in terms of precedence, the compiler reads right to left.
+
+3. The advantage of using pointers is that a) You can have a string with an undefined length. b) Pass variables by reference rather than value.
+
+4.1 char a[3] = "abc"; for a string
+4.2 Invalid because you are trying to declare an array with a string, then using a - instead of a =
+4.3 Invalid because you are trying to set a character from a string(end of string character) to an integer
+4.4 Pointer- int *a = variable; Points to the variable address
+4.5 Invalid because arrays already pass by refernce 
+4.6 Pointer- int *p = variable; Points to the variable address
+4.7 Refernce- scanf("%d", &variable); You are giving the function the address of the variable so it can be used in a pointer.
+4.8 *++argv; increases the value that argv is pointing to by 1 after the operation is complete.
+4.9 Reference- fxn(&main); you are sending the address of the main variable to the function so that it can be used as a pointer.
+4.10 sizeof(str); used to find the size of a string in terms of bytes.

reverse.c

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+/*Sean Kee*/
+/*Reverse inputted string using pointers*/
+#include <stdio.h>
+#include <string.h>
+
+void stringReverse(char string[]) {
+	char swap;
+	char *beginptr = &string[0];
+	char *endptr = &string[strlen(string) - 1];
+
+	while (beginptr < endptr) {
+		swap = *beginptr;
+		*beginptr = *endptr;
+		*endptr = swap;
+		beginptr++;
+		endptr--;
+	}
+
+	printf("New String: %s\n", string);
+
+}
+
+int main() {
+	char input[100];
+	printf("Input a string\n#: ");
+	fgets(input, sizeof(input), stdin);
+	input[strlen(input)-1] = '\0';
+	stringReverse(input);
+
+	return 0;
+}

strfxn.c

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+/*Sean Kee*/
+/*String Functions*/
+
+#include <stdio.h>
+
+void stringcat(char *str1, char *str2) {
+	while (*str1 != '\n') {
+		str1++;
+	}
+	while (*str2 != '\n') {
+		*str1 = *str2;
+		str2++;
+		str1++;
+	}
+	*str1 = '\0';
+
+}
+
+int stringcmp(char *str1, char *str2) {
+	while (*str1 != '\n' || *str2 != '\n') {
+		if (*str1 == *str2) {
+			str1++;
+			str2++;
+		}
+		else 
+			return 1;
+	}
+	return 0;
+}
+
+int main() {
+	int menu = 1;
+	int option;
+	char input1[100];
+	char input2[100];
+	int returned;
+	printf("Input String 1\n#: ");
+	fgets(input1, sizeof(input1), stdin);
+	printf("Input String 2\n#: ");
+	fgets(input2, sizeof(input2), stdin);
+
+	while (menu == 1) {
+		printf("\nWhat would you like to do?\n1: Concatenate Strings\n2: Compare Strings\n3: Exit\n#: ");
+		scanf("%d", &option);
+		switch(option) {
+			case 1:
+				stringcat(input1, input2);
+				printf("\nNew String: %s\n", input1);
+				break;
+			case 2:
+				returned = stringcmp(&input1, &input2);
+				if (returned == 0)
+					printf("\nIdentical Strings\n");
+				else
+					printf("\nNot Identical Strings\n");
+				break;
+			case 3:
+				menu = 0;
+				break;
+		}
+	}
+}