从给定方程a + b = c中找到缺失值

给定以下形式的方程式：

a + b = c 
 

其中任何一项$a$ ， $b$或者$c$不见了。任务是找到缺失的术语。

例子：

Input: 2 + 6 = ?
Output: 8

Input: ? + 3 =6
Output: 3

方法：只需使用等式即可找到缺失的数字$a + b = c$ 。首先，我们将从给定的方程式中找到两个已知的数字(在程序中以字符串形式读取)并将其转换为整数并放入方程式中。这样，我们可以找到第三个缺失的数字。我们可以通过将方程存储到字符串来实现它。

以下是逐步算法：

• 从空格位置将字符串拆分为较小的字符串，然后存储在数组中。这样数组将包含：

arr[0] = "a"
arr[1] = "+"
arr[2] = "b"
arr[3] = "="
arr[4] = "c"

• 丢失的字符可能出现在向量中的0或2或4位置。查找丢失字符的位置。
• 将已知字符转换为整数。
• 使用公式查找丢失的字符。

下面是上述方法的实现：

C++

// C++ program to find the missing number
// in the equation a + b = c
#include 
using namespace std;
 
// Function to find the missing number
// in the equation a + b = c
int findMissing(string str)
{
    // Array of string to store individual strings
    // after splitting the strings from spaces
    string arrStr[5];
     
    // Using stringstream to read a string object
    // and split
    stringstream ss(str);
     
    int i = 0;
     
    while (ss.good() && i < 5) {
        ss >> arrStr[i];
        ++i;
    }
     
    int pos = -1;
     
    // Find position of missing character
    if(arrStr[0] == "?")
        pos = 0;
    else if(arrStr[2] == "?")
        pos = 2;
    else
        pos = 4;
     
    if(pos == 0)
    {
        string b,c;
        b = arrStr[2];
        c = arrStr[4];
         
        // Using stoi() to convert strings to int
        int a = stoi(c) - stoi(b);
         
        return a;
    }
    else if(pos==2)
    {
        string a,c;
        a = arrStr[0];
        c = arrStr[4];
         
        // Using stoi() to convert strings to int
        int b = stoi(c) - stoi(a);
         
        return b;
    }
    else if(pos == 4)
    {
        string b,a;
        a = arrStr[0];
        b = arrStr[2];
         
        // Using stoi() to convert strings to int
        int c = stoi(a) + stoi(b);
         
        return c;
    }
}
 
// Driver code
int main()
{
    // Equation with missing value
    string str = "? + 3 = 7";
     
    cout<

---

Java

// Java program to find the missing number
// in the equation a + b = c
import java.util.*;
 
class GFG{
 
// Function to find the missing number
// in the equation a + b = c
static int findMissing(String str)
{
     
    // Array of String to store individual
    // strings after splitting the strings
    // from spaces
    String arrStr[] = str.split(" ");
 
    int pos = -1;
      
    // Find position of missing character
    if (arrStr[0].equals("?"))
        pos = 0;
    else if (arrStr[2].equals("?"))
        pos = 2;
    else
        pos = 4;
         
    if (pos == 0)
    {
        String b, c;
        b = arrStr[2];
        c = arrStr[4];
          
        // Using Integer.parseInt() to
        // convert strings to int
        int a = Integer.parseInt(c) -
                Integer.parseInt(b);
          
        return a;
    }
     
    else if (pos == 2)
    {
        String a, c;
        a = arrStr[0];
        c = arrStr[4];
          
        // Using Integer.parseInt() to
        // convert strings to int
        int b = Integer.parseInt(c) -
                Integer.parseInt(a);
          
        return b;
    }
     
    else if (pos == 4)
    {
        String b, a;
        a = arrStr[0];
        b = arrStr[2];
          
        // Using Integer.parseInt() to
        // convert strings to int
        int c = Integer.parseInt(a) +
                Integer.parseInt(b);
          
        return c;
    }
    return 0;
}
  
// Driver code
public static void main(String []args)
{
     
    // Equation with missing value
    String str = "? + 3 = 7";
      
    System.out.print(findMissing(str));
}
}
 
// This code is contributed by pratham76

Python3

# Python3 program to find the missing number
# in the equation a + b = c
   
# Function to find the missing number
# in the equation a + b = c
def findMissing(s):
 
    # Array of string to store individual strings
    # after splitting the strings from spaces
    arrStr = s.split()
       
    # Using stringstream to read a string object
    # and split
    pos = -1;
       
    # Find position of missing character
    if(arrStr[0] == "?"):
        pos = 0;
    elif(arrStr[2] == "?"):
        pos = 2;
    else:
        pos = 4;
       
    if(pos == 0):
         
        b = arrStr[2];
        c = arrStr[4];
           
        # Using int() to convert strings to int
        a = int(c) - int(b);
           
        return a;
     
    elif(pos == 2):
     
        a = arrStr[0];
        c = arrStr[4];
           
        # Using int() to convert strings to int
        b = int(c) - int(a);
           
        return b;
     
    elif(pos == 4):
     
        a = arrStr[0];
        b = arrStr[2];
           
        # Using int() to convert strings to int
        c = int(a) + int(b);
           
        return c;
       
# Driver code
if __name__=='__main__':
     
    # Equation with missing value
    s = "? + 3 = 7";
     
    print(findMissing(s))
 
    # This code is contributed by rutvik_56

C#

// C# program to find the missing number
// in the equation a + b = c
using System;
class GFG
{
 
    // Function to find the missing number
    // in the equation a + b = c
    static int findMissing(string str)
    {
 
        // Array of String to store individual
        // strings after splitting the strings
        // from spaces
        string[] arrStr = str.Split(" ");
        int pos = -1;
 
        // Find position of missing character
        if (arrStr[0].Equals("?"))
            pos = 0;
        else if (arrStr[2].Equals("?"))
            pos = 2;
        else
            pos = 4;
        if (pos == 0)
        {
            string b, c;
            b = arrStr[2];
            c = arrStr[4];
 
            // Using Integer.parseInt() to
            // convert strings to int
            int a = int.Parse(c) - int.Parse(b);
            return a;
        }
        else if (pos == 2)
        {
            string a, c;
            a = arrStr[0];
            c = arrStr[4];
 
            // Using Integer.parseInt() to
            // convert strings to int
            int b = int.Parse(c) - int.Parse(a);
            return b;
        }
 
        else if (pos == 4)
        {
            string b, a;
            a = arrStr[0];
            b = arrStr[2];
 
            // Using Integer.parseInt() to
            // convert strings to int
            int c = int.Parse(a) + int.Parse(b);
            return c;
        }
        return 0;
    }
 
    // Driver code
    public static void Main(string[] args)
    {
 
        // Equation with missing value
        string str = "? + 3 = 7";
        Console.WriteLine(findMissing(str));
    }
}
 
// This code is contributed by chitranayal.

输出：

4