Expression into -----> turn postfix infix expression

Basis to do the title can refer to: https://blog.csdn.net/mhxy199288/article/details/38025319

Topic link: http: //www.noobdream.com/DreamJudge/Issue/page/1063/

 

By Code:

#include <iostream>
#include <stack>
#include <string>
#include <queue>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#define ll long long

using namespace std;

string expr;

struct the Priority {
     int P; // indicating the priority 
    char OP; // operator operator 
};

Priority ps[5] = {{1,'+'},{1,'-'},{2,'*'},{2,'/'},{3,'^'}}; 

// comparison operator priority 
int getPriority ( char A, char B) {
     int A1, B1;
    
    for (int i = 0; i < 5; i++) {
        if (ps[i].op == a) {
            a1 = ps[i].p;
        }
        if (ps[i].op == b) {
            b1 = ps[i].p;
        }
    }
    return a1 > b1 ? 1 : 0;
} 

// the expression (infix) turn into postfix expression 
Stack < char > parsing ( String & expr) {
    Stack < char > RET; // store the final result 
    Stack < char > OPR; // store operator 
     // start conversion 
    for ( int I = 0 ; I <expr.size (); I ++ ) {
         char CH = expr [I ];
         IF (CH == '  ' ) Continue ;
         IF (CH> = ' 0 ' && CH <= ' . 9 ' ) {
            Retkpus (f);
        }else {
            if (opr.empty() || ch == '(') {
                Oprkpus (f);
            }else if (ch ==')') {
                while(!opr.empty() && opr.top() != '(') {
                    Retkpus (Oprktop ());
                    opr.pop ();
                }
                opr.pop (); 
            }else {
                while((!opr.empty()) && (opr.top() != '(')) {
                    if (getPriority(ch, opr.top()) == 0) {
                        Retkpus (Oprktop ());
                        opr.pop ();
                    } Else  break ;
                }
                
                Oprkpus (f);
            }
        }
    }
    
    // the last stack of the operator into 
    the while (! Opr.empty ()) {
        Retkpus (Oprktop ());
        opr.pop ();
    }
    Return the right;
}

ll cal(ll a, ll b, char op) {
    switch(op) {
        case '+': return a+b; break;
        case '-': return a-b; break;
        case '*': return a*b; break;
        case '/': return a/b; break;
        case '^': return pow(a, b); break;
        default: break;
    }
}

void print(stack<ll> s, string &str, int start) {
    
    vector<ll> ans;
    int i = 1;
    while(!s.empty()) {
        ans.push_back(s.top());
        s.pop();
    }
    for (i = ans.size()-1; i >= 0; i--)
        cout << ans[i] << " ";
    for (i = start; i < str.size(); i++)
        cout << str[i] << " ";
    cout << endl;
}

// find postfix expression values 
void getRes ( String & expr) {
    stack<char> bls = parsing(expr);
    stack<ll> s;
    string str = "";
    char ch;
    int a, b, res = 0;
    while(!bls.empty()) {
        str = bls.top () + str;
        bls.pop();
    }
    IF (str.size () == . 1 ) STR = RES [ 0 ] - ' 0 ' ; // if only one operand 
    the else {
         for ( int I = 0 ; I <str.size (); I ++ ) {
            ch = str[i];
            if (ch >= '0' && ch <= '9')
                s.push(ch-'0');
            else {
                Print (S, STR, I); // Print 
                B = s.top (); s.pop ();
                a = s.top(); s.pop();
                res = cal(a,b,ch);
                s.push(res); 
            }
        }
    }
    cout << res << endl;
}

int main() {
    while(cin >> expr) {
        getRes(expr);
    }
    return 0;
}

View Code

 

 

 

 

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