有沒有辦法讓我的程序將字符轉換爲整數？

Question

我一直在運行這個並輸入「12+」作爲表達式。試圖添加頂部值和下一個值，它一直給我結果'c'，但我希望結果是3.那麼有什麼辦法讓我的程序將char'c'轉換爲int' 3'和char'd'到int 4等等？

//array based stack implementation 
class Stack 
{ 
private: 
    int capacity;  //max size of stack 
    int top;   //index for top element 
    char *listArray;  //array holding stack elements 

public: 
    Stack (int size = 50){ //constructor 
     capacity = size; 
     top = 0; 
     listArray = new char[size]; 
    } 

    ~Stack() { delete [] listArray; } //destructor 


    void push(char it) { //Put "it" on stack 
     listArray[top++] = it; 
    } 
    char pop() { //pop top element 
     return listArray [--top]; 
    } 

    char& topValue() const { //return top element 
     return listArray[top-1]; 
    } 

    char& nextValue() const {//return second to top element 
     return listArray[top-2]; 
    } 


    int length() const { return top; } //return length 



}; 

int main() 
{ 
    string exp; 
    char it = ' '; 
    int count; 
    int push_length; 


    cout << "Enter an expression in postfix notation:\n"; 
    cin >> exp; 
    cout << "The number of characters in your expression is " << exp.length() << ".\n"; 
    Stack STK; 

    for(count= 0; count < exp.length() ;count++) 
    { 

     if (exp[count] == '+') 
     { 
      it = exp[count - 1]; 
      cout << it << "?\n"; 

       while (!isdigit(it)) 
     { 
      cout << it << "!\n"; 
      it = exp[count--]; 
     } 

     STK.push(it); 
     cout << STK.topValue() << "\n"; 


     it = exp[count - 2]; 
     cout << it << "\n"; 

     if (isdigit(it)) 
     { 
      STK.push(it); 

     } 
     cout << STK.topValue() << "\n"; 
     cout << STK.nextValue() << "\n"; 
     it = STK.topValue() + STK.nextValue(); 
     cout << it << "\n"; 

     STK.pop(); 
     STK.pop(); 
     STK.push(it); 
     cout << STK.topValue() << "\n"; 

     } 


    } 
    cout << "The number of characters pushed into the stack is " << STK.length() << ".\n"; 
    push_length = STK.length(); 
    return(0); 
} 

Answer 1

你可以做這樣的事情：[？我可以以某種方式得到我的程序字符轉換爲整數]

char ch='d'; //ch is the character to convert 
int i=1+(ch-'a');