20. Valid Parentheses.c

/*
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:
    Open brackets must be closed by the same type of brackets.
    Open brackets must be closed in the correct order.
    Note that an empty string is also considered valid.

Example 1:
    Input: "()"
    Output: true


Example 2:
    Input: "()[]{}"
    Output: true


Example 3:
    Input: "(]"
    Output: false


Example 4:
    Input: "([)]"
    Output: false


Example 5:
    Input: "{[]}"
    Output: true
*/

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

int STACK_NODE_NUMBER_PER_TIME = 20;

typedef char StackNode;
typedef struct {
    int _length;
    StackNode *_top;
    StackNode *_stack;
} Stack;

int stackIsEmpty(Stack *stack) {
    return stack->_top == stack->_stack;
}

void stackPush(Stack *stack, StackNode node) {
    if (!stack->_stack) {
        stack->_stack = (StackNode *)malloc(sizeof(StackNode) * STACK_NODE_NUMBER_PER_TIME);
        stack->_top = stack->_stack;
        stack->_length = STACK_NODE_NUMBER_PER_TIME;
    }

    if ((stack->_top - stack->_stack) / sizeof(StackNode) > (stack->_length - 1)) {
        int length = stack->_length;
        stack->_stack = (StackNode *)realloc(stack->_stack, sizeof(StackNode) * (length + STACK_NODE_NUMBER_PER_TIME));
        stack->_top = stack->_stack + length;
        stack->_length = length + STACK_NODE_NUMBER_PER_TIME;
    }

    *stack->_top++ = node;
}

StackNode stackPop(Stack *stack) {
    if (stackIsEmpty(stack)) {
        return '\\';
    }
    return *(--stack->_top);
}

int stackCount(Stack *stack) {
    return (stack->_top - stack->_stack) / sizeof(StackNode);
}

StackNode stackPeekTop(Stack *stack) {
    return *(stack->_top - 1);
}

void destoryStack(Stack *stack) {
    if (stack->_stack) {
        free(stack->_stack);
        stack->_stack = NULL;
        stack->_top = stack->_stack;
    }
}

int isValid(char* string) {
    Stack stack;
    stack._length = 0;
    stack._stack = NULL;
    stack._top = stack._stack;
    StackNode val;

    int length = strlen(string);
    int i;
    for (i = 0; i < length; ++i) {
        char c = string[i];
        switch (c) {
            case '(':
            case '[':
            case '{':
                stackPush(&stack, c);
                break;
            case ')':
                val = stackPop(&stack);
                if (val != '(') {
                    destoryStack(&stack);
                    return 0;
                }
                break;
            case ']':
                val = stackPop(&stack);
                if (val != '[') {
                    destoryStack(&stack);
                    return 0;
                }
                break;
            case '}':
                val = stackPop(&stack);
                if (val != '{') {
                    destoryStack(&stack);
                    return 0;
                }
            break;
        }
    }
    int res = !length || stackIsEmpty(&stack);
    destoryStack(&stack);

    return res;
}

int main() {
    printf("%s\n", isValid("{{{{{{{{{{{{[[[[[[[[[[[[[") ? "true" : "false");
    printf("%s\n", isValid("{[]") ? "true" : "false");
    printf("%s\n", isValid("") ? "true" : "false");
    printf("%s\n", isValid("[([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([([()])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])])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? "true" : "false");

    return 0;
}