assignment problem 2

assignment1/problem2/validbrackets.c

@@ -0,0 +1,106 @@
+/*
+ * Author: Walter
+ * Student ID: 1930006025
+ * Assignment_1_problem_2
+ * validbrackets function
+ */
+
+#include <stddef.h>
+#include <string.h>
+
+#include "stack.h"
+#include "validbrackets.h"
+
+/* all the left brackets */
+static char LEFTBRACKETS[]  = "({[<";
+
+/* all the right brackets */
+static char RIGHTBRACKETS[] = ")}]>";
+
+/* number of brackets pairs */
+static int BRACKETS_LEN = 4;
+
+bool ValidBrackets(char *str) {
+
+	/* if string pass all the test, will return default value 'true' */
+	bool result = true;
+
+	/* null pointer will return false */
+	if (str == NULL) {
+		return false;
+	}
+	
+	/* tmp value to store the left brackets */
+	char left;
+	
+	/* length of string */
+	size_t str_len = strlen(str);
+
+	Stack stack;
+	/* only half length of the string is enougth,
+	 * empty stack is allowed */
+	CreateStack(&stack, str_len/2);
+
+	/* loop for all char in string */
+	for (size_t i=0; i<str_len; i++) {
+
+		/* full stack means the string is not vailed */
+		if (IsFull(&stack)) {
+			result = false;
+			break;
+		}
+
+		/* if it is not left brackets will return -1 */
+		if (IndexLeftBracket(str[i]) != -1) {
+			/* store the left brackets in stack */
+			Push(&stack, str[i]);
+		} else {
+			/* check empty stack before pop from stack */
+			if (IsEmpty(&stack)) {
+				result = false;
+				break;
+			}
+			/* get the pair left brackets from stack */
+			Pop(&stack, &left);
+
+			/* check if the left and right brackets matched */
+			if (!MatchBracket(left, str[i])) {
+				result = false;
+				break;
+			}
+		}
+	}
+	/* if finally the stack is not empty, return falsle */
+	if (!(IsEmpty(&stack))) {
+		result = false;
+	}
+	/* no memory leak */
+	DestroyStack(&stack);
+
+	return result;
+}
+
+int IndexLeftBracket(char c) {
+	for (int i=0; i<BRACKETS_LEN; i++) {
+		if (c == LEFTBRACKETS[i]) {
+			return i;
+		}
+	}
+	/* if c is not left brackets, return -1 */
+	return -1;
+}
+
+int IndexRightBracket(char c) {
+	for (int i=0; i<BRACKETS_LEN; i++) {
+		if (c == RIGHTBRACKETS[i]) {
+			return i;
+		}
+	}
+	/* if c is not right brackets, return -1 */
+	return -1;
+}
+
+bool MatchBracket(char left, char right) {
+	/* check whether left and right brackets are matched */
+	return IndexLeftBracket(left) == IndexRightBracket(right);
+}