编程实现表达式转换

原题链接：68729.这是笔记的地方
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盛sir

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2025-11-06 14:50:24

发布于：广东

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中转后

#include <bits/stdc++.h>
using namespace std;
stack<char> sufft;
stack<char> pret;
string suffs,pres;
int level(char c){
	if(c=='+'||c=='-') return 1;
	if(c=='*'||c=='/') return 2;
}
void suff(string s){
	for(int i=0;i<s.size();i++){
		if(s[i]>='a' && s[i]<='z'){
			suffs += s[i];
		}else if(s[i]=='('){
			sufft.push(s[i]);
		}else if(s[i]=='+'||s[i]=='-'||s[i]=='*'||s[i]=='/'){
			  if(sufft.empty() || sufft.top()=='('){
			  	sufft.push(s[i]);
			  }else{
			  	while(!sufft.empty() && sufft.top()!='(' && level(sufft.top()) >= level(s[i]))
			  		{
				     suffs += sufft.top();
			  		 sufft.pop();
				    }
				sufft.push(s[i]);
			  }
		}else if(s[i]==')'){
			while(sufft.top()!='('){
				suffs += sufft.top();
			  	sufft.pop();
			}
			sufft.pop();	
		}
	}
	while(!sufft.empty()){
		suffs += sufft.top();
		sufft.pop();
	}
}
int main(){
	string s1;
	cin >> s1;
	suff(s1);
	cout << suffs;
	return 0;
}

中转前

#include <bits/stdc++.h>
using namespace std;

int f1(char x) {
    if(x=='+'||x=='-')return 1;
    if(x=='*'||x=='/')return 2;
    return 0;
}

int f2(char x) {
    if(x=='+'||x=='-'||x=='*'||x=='/')return 1;
    return 0;
}

int main(){
    string a;
    cin>>a;
    reverse(a.begin(),a.end());
    for(int i=0;i<a.size();i++){
        if(a[i]=='(')a[i]=')';
        else if(a[i]==')')a[i]='(';
    }
    stack<char> s;
    string b="";
    for(int i=0;i<a.size();i++){
        char tmp=a[i];
        if(tmp>='a'&&tmp<='z'){
            b+=tmp;
        }else if(tmp=='('){
            s.push(tmp);
        }else if(tmp==')'){
            while(!s.empty()&&s.top()!='('){
                b+=s.top();
                s.pop();
            }
            if(!s.empty())s.pop();
        }else if(f2(tmp)){
            while(!s.empty()&&f1(s.top())>f1(tmp)){
                b+=s.top();
                s.pop();
            }
            s.push(tmp);
        }
    }
    while(!s.empty()){
        b+=s.top();
        s.pop();
    }
    reverse(b.begin(),b.end());
    cout<<b<<endl;
    return 0;
}

中转前后

#include <bits/stdc++.h>
using namespace std;
stack<char> sufft;
stack<char> pret;
string suffs,pres;
int level(char c){
	if(c=='+'||c=='-') return 1;
	if(c=='*'||c=='/') return 2;
}
void suff(string s){
	for(int i=0;i<s.size();i++){
		if(s[i]>='a' && s[i]<='z'){
			suffs += s[i];
		}else if(s[i]=='('){
			sufft.push(s[i]);
		}else if(s[i]=='+'||s[i]=='-'||s[i]=='*'||s[i]=='/'){
			  if(sufft.empty() || sufft.top()=='('){
			  	sufft.push(s[i]);
			  }else{
			  	while(!sufft.empty() && sufft.top()!='(' && level(sufft.top()) >= level(s[i]))
			  		{
				     suffs += sufft.top();
			  		 sufft.pop();
				    }
				sufft.push(s[i]);
			  }
		}else if(s[i]==')'){
			while(sufft.top()!='('){
				suffs += sufft.top();
			  	sufft.pop();
			}
			sufft.pop();	
		}
	}
	while(!sufft.empty()){
		suffs += sufft.top();
		sufft.pop();
	}
}
void pre(string s){
	for(int i=s.size()-1;i>=0;i--){
		if(s[i]>='a' && s[i]<='z'){
			pres += s[i];
		}else if(s[i]==')'){
			pret.push(s[i]);
		}else if(s[i]=='+'||s[i]=='-'||s[i]=='*'||s[i]=='/'){
			  if(pret.empty() || pret.top()==')'){
			  	pret.push(s[i]);
			  }else{
			  	while(!pret.empty() && pret.top()!=')' && level(pret.top()) >= level(s[i]))
			  		{
				     pres += pret.top();
			  		 pret.pop();
				    }
				pret.push(s[i]);
			  }
		}else if(s[i]=='('){
			while(pret.top()!=')'){
				pres += pret.top();
			  	pret.pop();
			}
			pret.pop();	
		}
	}
	while(!pret.empty()){
		pres += pret.top();
		pret.pop();
	}
}
int main(){
	string s1;
	cin >> s1;
	suff(s1);
	pre(s1);
	
	reverse(pres.begin(),pres.end());
	cout << pres<<endl;
	cout << suffs<<endl;
	return 0;
}

前转后

#include<bits/stdc++.h>
using namespace std;
stack<char> sufft;
string suffs;
const int maxSize = 109;
int level(char c) {
	if (c == '+' || c == '-')
		return 1; 
	else
		return 2;
}
void suff(string s){
	for(int i=0;i<s.size();i++){
		if(s[i]>='a' && s[i]<='z'){
			suffs += s[i];
		}else if(s[i]=='('){
			sufft.push(s[i]);
		}else if(s[i]=='+'||s[i]=='-'||s[i]=='*'||s[i]=='/'){
			  if(sufft.empty() || sufft.top()=='('){
			  	sufft.push(s[i]);
			  }else{
			  	while(!sufft.empty() && sufft.top()!='(' && level(sufft.top()) >= level(s[i]))
			  		{
				     suffs += sufft.top();
			  		 sufft.pop();
				    }
				sufft.push(s[i]);
			  }
		}else if(s[i]==')'){
			while(sufft.top()!='('){
				suffs += sufft.top();
			  	sufft.pop();
			}
			sufft.pop();	
		}
	}
	while(!sufft.empty()){
		suffs += sufft.top();
		sufft.pop();
	}
}
int main() {
	string s;
	cin >> s;
	stack<string> num;
	for (int i = s.length() - 1; i >= 0; i--) {
		if (s[i] >= 'a' && s[i] <= 'z') {
			num.push(string(1,s[i]));
		}
		else {
			string l = num.top(); num.pop();
			string r = num.top(); num.pop();
			string ans = "(" + l + s[i] + r + ")";
			num.push(ans);
		}
	}	
	suff(num.top());
	cout << suffs;

	return 0;
}

#include<bits/stdc++.h>
using namespace std;

int main() {
	string s;
	cin >> s;
	stack<int> num;
	for (int i = 0; i < s.length(); i++) {
		if (s[i] >= '0' && s[i] <= '9') {
			num.push(s[i] - '0');
		}
		else {
			int r = num.top(); num.pop();
			int l = num.top(); num.pop();
			if (s[i] == '+') num.push(l + r);
			else if (s[i] == '-') num.push(l - r);
			else if (s[i] == '*') num.push(l * r);
			else num.push(l / r);
		}
	}
	cout << num.top();
	return 0;
}


#include<bits/stdc++.h>
using namespace std;

int main() {
	string s;
	cin >> s;
	stack<int> st;
	for (int i = s.length()-1; i >= 0; i--) {
		if (s[i] >= '0' && s[i] <= '9') {
			st.push(s[i] - '0');
		}
		else {
			int l = st.top(); st.pop();
			int r = st.top(); st.pop();
			if (s[i] == '+') {
				st.push(l + r);
			}
			else if (s[i] == '-') {
				st.push(l - r);
			}
			else if (s[i] == '*') {
				st.push(l * r);
			}
			else if (s[i] == '/') {
				st.push(l / r);
			}
		}
	}
	cout << st.top();
	return 0;
}

#include<bits/stdc++.h>
using namespace std;

stack<int> num;
stack<char> op;
int getPriority(char op) {
	if (op == '+' || op == '-')
		return 0; //+或-的优先级比较低
	return 1;
}
void calc() {
	int r = num.top(); num.pop();//栈顶是右操作数
	int l = num.top(); num.pop();//次栈顶是左操作数
	if (op.top() == '+') num.push(l + r);
	if (op.top() == '-') num.push(l - r);
	if (op.top() == '/') num.push(l / r);
	if (op.top() == '*') num.push(l * r);
	op.pop();//弹出运算符
}
int main() {
	string s;
	cin >> s;
	for (int i = 0; i < s.length(); i++) {
		if (s[i] >= '0' && s[i] <= '9') {
			num.push(s[i] - '0');
		}
		else {
			if (s[i] == '(') {
				op.push(s[i]);//左括号直接进栈
			}
			else if (s[i] == '+'||s[i]=='-'||s[i]=='*'||s[i]=='/') {
				while (op.size() && op.top()!='('&&getPriority(op.top()) >= getPriority(s[i])) {
					calc();
				}
				op.push(s[i]);
			}
			else if (s[i] == ')') {
				while (op.top() != '(') {
					calc();
				}
				op.pop();//弹出左括号
			}
		}
	}
	while (op.size()) {
		calc();
	}
	cout << num.top();
	return 0;
}
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