leetcode224

Love The Way You Lie 2022-08-09 00:51 131阅读 0赞

Basic Calculator

折腾了好一会儿，其实意思很简单。就是实现一个包含+，-法和括号运算的计算器。

可能是没找对方法吧，看了网上的代码量，感觉我写的就是一坨屎啊。。。参考：http://blog.csdn.net/xudli/article/details/46554835

每次压栈都是当前的结果，这样计算量会小很多。不过比较起来大神的代码比较简单，我的思路还是比较清晰的。

我的代码：

class Solution {
    public:
    	int calculate(string s) {
    		stack<int>myStack;
    		stack<char>myOperator;
    		int i;
    		for (i = 0; i<s.length(); i++)
    		{
    			while (i < s.length() && s[i] == ' ')
    				i++;
    			if (i == s.length())
    				break;
    			if (s[i] == '+' || s[i] == '-' || s[i] == '(')
    				myOperator.push(s[i]);
    			else if(s[i] == ')')
    			{
    				while ( myOperator.top() != '(')
    				{
    					int element1 = myStack.top();
    					myStack.pop();
    					int element2 = myStack.top();
    					myStack.pop();
    					char op = myOperator.top();
    					myOperator.pop();
    					if (op == '+')
    						myStack.push(element1 + element2);
    					else if (op == '-')
    						myStack.push(element2 - element1);
    				}
    				if (!myOperator.empty())
    					myOperator.pop();
    				while (!myOperator.empty() && (myOperator.top() != '('))
    				{
    					int element1 = myStack.top();
    					myStack.pop();
    					int element2 = myStack.top();
    					myStack.pop();
    					char op = myOperator.top();
    					myOperator.pop();
    					if (op == '+')
    						myStack.push(element1 + element2);
    					else if (op == '-')
    						myStack.push(element2 - element1);
    				}
    			}
    			else
    			{
    				//myStack.push(getNumber(s, i));
    				long long int number = 0;
    				int j = i;
    				while (j<s.length() && (s[j]-'0'<=9)&&(s[j]-'0'>=0))
    				{
    					number = number * 10 + (s[j] - '0');
    					j++;
    				}
    				i = j - 1;
    				myStack.push(number);
    				while (!myOperator.empty() && (myOperator.top() != '('))
    				{
    					int element1 = myStack.top();
    					myStack.pop();
    					int element2 = myStack.top();
    					myStack.pop();
    					char op = myOperator.top();
    					myOperator.pop();
    					if (op == '+')
    						myStack.push(element1 + element2);
    					else if (op == '-')
    						myStack.push(element2 - element1);
    				}
    				//if (!myOperator.empty())
    					//myOperator.pop();
    			}
    		}
    		return myStack.top();
    	}
    };