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history_source/信息学奥赛一本通/3.1.6.cpp

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+#include<cstdio>
+#include<map>
+#include<cstdlib>
+struct Node
+{
+	union
+	{
+		char f;
+		int num;
+	};
+	bool flag;
+};
+namespace myDef
+{
+	template<class T_queue>
+	struct Node_queue
+	{
+		T_queue num;
+		Node_queue *next=0;
+	};
+	template<class a_queue>
+	struct queue
+	{
+		Node_queue<a_queue> *head=0,*tail=0,*L=0;
+		bool isn=0;
+		int SIZE_queue;
+		void beginning()
+		{
+			head=tail=new Node_queue<a_queue>;
+			tail->next=head;
+			SIZE_queue=0;
+			isn=1;
+		}
+		queue()
+		{
+			beginning();
+		} 
+		queue(a_queue *left,a_queue *right)
+		{
+			beginning();
+			a_queue *p=left;
+			while(p!=right)
+			{
+				push(*p);
+				p++;
+			}
+		}
+		bool push(a_queue s)
+		{
+			SIZE_queue++;
+			tail->num=s;
+			if(tail->next==head)
+			{
+				tail->next=new Node_queue<a_queue>;
+				tail->next->next=head;
+				L=tail;
+				tail=tail->next;
+				return 1;
+			}
+			L=tail;
+			tail=tail->next;
+			return 0;
+		}
+		bool pop()
+		{
+			if(head==tail) return 1;
+			head=head->next;
+			SIZE_queue--;
+			return 0;
+		} 
+		a_queue& front()
+		{
+			return head->num;
+		} 
+		a_queue& back()
+		{
+			return L->num;
+		}
+		int size()
+		{
+			return SIZE_queue;
+		}
+	};
+}
+using myDef::queue;
+using std::map;
+map<char,int>opf;
+queue<Node>back_operation;
+char ops[45]={'\0'};
+int top=0;
+void error()
+{
+	printf("NO\n");
+	exit(0);
+}
+bool isop(char n)
+{
+	switch(n)
+	{
+		case '+':return 1;
+		case '-':return 1;
+		case '*':return 1;
+		case '/':return 1;
+	}
+	return 0;
+}
+void mid_to_back_operation()
+{
+	int num=0;
+	char li,back='+';
+	Node node;
+	while(li=getchar(),li!='@')
+	{
+		if(li>='0'&&li<='9') 
+		{
+			num_op:
+				if(num>=0) num=num*10+li-'0';
+				else num=num*10-(li-'0');
+		}
+		else
+		{
+			if(isop(back)&&li=='-') 
+			{
+				li=getchar();
+				back=li;
+				if(!(li>='0'&&li<='9')) error();
+				li-='0';
+				li=-li;
+				li+='0';
+				goto num_op;
+			}
+			if(li=='(')
+			{
+				if(!isop(back)) error();
+				ops[top++]=li;
+			}
+			else
+			{
+				if(back!=')')
+				{
+					node.num=num;
+					node.flag=1;
+					back_operation.push(node);
+					num=0;
+				}
+			}
+			if(li==')')
+			{
+				while(ops[top-1]!='(')
+				{
+					node.flag=0;
+					node.f=ops[top-1];
+					back_operation.push(node);
+					top--;
+				}
+				top--;
+			}
+			if(li!='('&&li!=')')
+			{
+				if(isop(back)) error();
+				while(top>0&&opf[li]<=opf[ops[top-1]])
+				{
+					node.f=ops[top-1];
+					node.flag=0;
+					back_operation.push(node);
+					top--;
+				}
+				ops[top++]=li;
+			}
+		}
+		back=li; 
+	}
+	if(back!=')') 
+	{
+		node.num=num;
+		node.flag=1;
+		back_operation.push(node);
+	}
+	while(top>=0)
+	{
+		node.flag=0;
+		node.f=ops[top-1];
+		back_operation.push(node);
+		top--;
+	}
+}
+int operation()
+{
+	int zhan[35],a,b;
+	top=0;
+	Node li;
+	while(back_operation.size()>0)
+	{
+		li=back_operation.front();
+		if(li.flag) zhan[top++]=li.num;
+		else
+		{
+			a=zhan[top-2];
+			b=zhan[top-1];
+			top--;
+			switch(li.f)
+			{
+				case '+':zhan[top-1]=a+b;break;
+				case '-':zhan[top-1]=a-b;break;
+				case '*':zhan[top-1]=a*b;break;
+				case '/':
+					if(b==0) error();
+					zhan[top-1]=a/b;break;
+			}
+		}
+		back_operation.pop();
+	}
+	return zhan[0];
+}
+int main()
+{
+	opf['*']=2;
+	opf['/']=2;
+	opf['+']=1;
+	opf['-']=1;
+	opf['(']=-1;
+	mid_to_back_operation();
+	printf("%d\n",operation());
+	return 0;
+}