Find the missing value from the given equation a + b = c
Last Updated :
01 Sep, 2022
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Given an equation of the form:
a + b = c
Out of which any one of the terms
Examples:
Input: 2 + 6 = ? Output: 8 Input: ? + 3 =6 Output: 3
Approach:
Missing numbers can be found simply using the equation
Below is the step by step algorithm:
- Split the string into smaller strings from the position of spaces and store in an array. So that the array will contain:
arr[0] = "a" arr[1] = "+" arr[2] = "b" arr[3] = "=" arr[4] = "c"
- The missing character can occur at position 0 or 2 or 4 in the vector. Find the position of missing character.
- Convert known characters to integers.
- Find missing character using the equation.
Below is the implementation of the above approach:
// C++ program to find the missing number
// in the equation a + b = c
#include <bits/stdc++.h>
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<<findMissing(str);
return 0;
}
// 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 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# 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.
<script>
// JavaScript program to find the missing number
// in the equation a + b = c
// Function to find the missing number
// in the equation a + b = c
function findMissing(str)
{
// Array of String to store individual
// strings after splitting the strings
// from spaces
let arrStr = str.split(" ");
let pos = -1;
// Find position of missing character
if (arrStr[0]==("?"))
pos = 0;
else if (arrStr[2]==("?"))
pos = 2;
else
pos = 4;
if (pos == 0)
{
let b, c;
b = arrStr[2];
c = arrStr[4];
// Using Integer.parseInt() to
// convert strings to int
let a = parseInt(c) -
parseInt(b);
return a;
}
else if (pos == 2)
{
let a, c;
a = arrStr[0];
c = arrStr[4];
// Using Integer.parseInt() to
// convert strings to int
let b = parseInt(c) -
parseInt(a);
return b;
}
else if (pos == 4)
{
let b, a;
a = arrStr[0];
b = arrStr[2];
// Using Integer.parseInt() to
// convert strings to int
let c = parseInt(a) +
parseInt(b);
return c;
}
return 0;
}
// Driver code
// Equation with missing value
let str = "? + 3 = 7";
document.write(findMissing(str));
// This code is contributed by rag2127
</script>
Output
4
Complexity Analysis:
- Time Complexity: O(1)
- Auxiliary Space: O(1)
