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Find the original coordinates whose Manhattan distances are given
  • Difficulty Level : Medium
  • Last Updated : 11 May, 2021

Given the Manhattan distances of three coordinates on a 2-D plane, the task is to find the original coordinates. Print any solution if multiple solutions are possible else print -1.
 

Input: d1 = 3, d2 = 4, d3 = 5 
Output: (0, 0), (3, 0) and (1, 3) 
Manhattan distance between (0, 0) to (3, 0) is 3, 
(3, 0) to (1, 3) is 5 and (0, 0) to (1, 3) is 4
Input: d1 = 5, d2 = 10, d3 = 12 
Output: -1 
 

 

Approach: Let’s analyze when no solution exists. First the triangle inequality must hold true i.e. the largest distance should not exceed the sum of other two. Second, sum of all Manhattan distances should be even. 
Here’s why, if we have three points and their x-coordinates are x1, x2 and x3 such that x1 < x2 < x3. They will contribute to the sum (x2 – x1) + (x3 – x1) + (x3 – x2) = 2 * (x3 – x1). Same logic applied for y-coordinates. 
In all the other cases, we have a solution. Let d1, d2 and d3 be the given Manhattan distances. Fix two points as (0, 0) and (d1, 0). Now since two points are fixed, we can easily find the third point as x3 = (d1 + d2 – d3) / 2 and y3 = (d2 – x3).
Below is the implementation of the above approach: 
 

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the original coordinated
void solve(int d1, int d2, int d3)
{
 
    // Maximum of the given distances
    int maxx = max(d1, max(d2, d3));
 
    // Sum of the given distances
    int sum = (d1 + d2 + d3);
 
    // Conditions when the
    // solution doesn't exist
    if (2 * maxx > sum or sum % 2 == 1) {
        cout << "-1";
        return;
    }
 
    // First coordinate
    int x1 = 0, y1 = 0;
 
    // Second coordinate
    int x2 = d1, y2 = 0;
 
    // Third coordinate
    int x3 = (d1 + d2 - d3) / 2;
    int y3 = (d2 + d3 - d1) / 2;
    cout << "(" << x1 << ", " << y1 << "), ("
         << x2 << ", " << y2 << ") and ("
         << x3 << ", " << y3 << ")";
}
 
// Driver code
int main()
{
    int d1 = 3, d2 = 4, d3 = 5;
    solve(d1, d2, d3);
 
    return 0;
}

Java




// Java implementation of the approach
import java .io.*;
 
class GFG
{
     
// Function to find the original coordinated
static void solve(int d1, int d2, int d3)
{
 
    // Maximum of the given distances
    int maxx = Math.max(d1, Math.max(d2, d3));
 
    // Sum of the given distances
    int sum = (d1 + d2 + d3);
 
    // Conditions when the
    // solution doesn't exist
    if (2 * maxx > sum || sum % 2 == 1)
    {
        System.out.print("-1");
        return;
    }
 
    // First coordinate
    int x1 = 0, y1 = 0;
 
    // Second coordinate
    int x2 = d1, y2 = 0;
 
    // Third coordinate
    int x3 = (d1 + d2 - d3) / 2;
    int y3 = (d2 + d3 - d1) / 2;
    System.out.print("("+x1+", "+y1+"), ("+x2+", "+y2+") and ("+x3+", "+y3+")");
}
 
// Driver code
public static void main(String[] args)
{
    int d1 = 3, d2 = 4, d3 = 5;
    solve(d1, d2, d3);
 
}
}
 
// This code is contributed by anuj_67..

Python3 





# Python3 implementation of the approach

# Function to find the original coordinated
def solve(d1, d2, d3) :

    
    # Maximum of the given distances
    maxx = max(d1, max(d2, d3))
    
    # Sum of the given distances
    sum = (d1 + d2 + d3)
    
    # Conditions when the
    # solution doesn't exist
    if (2 * maxx > sum or sum % 2 == 1) :
        print("-1")
        return
    
    
    # First coordinate
    x1 = 0
    y1 = 0
    
    # Second coordinate
    x2 = d1 
    y2 = 0
    
    # Third coordinate
    x3 = (d1 + d2 - d3) // 2
    y3 = (d2 + d3 - d1) // 2
    print("(" , x1 , "," , y1 , "), ("
        , x2 , "," , y2 , ") and ("
        , x3 , "," , y3 , ")")


# Driver code
d1 = 3
d2 = 4
d3 = 5
solve(d1, d2, d3)

# This code is contributed by ihritik


C#




// C# implementation of the approach
using System;
 
class GFG
{
     
// Function to find the original coordinated
static void solve(int d1, int d2, int d3)
{
 
    // Maximum of the given distances
    int maxx = Math.Max(d1, Math.Max(d2, d3));
 
    // Sum of the given distances
    int sum = (d1 + d2 + d3);
 
    // Conditions when the
    // solution doesn't exist
    if (2 * maxx > sum || sum % 2 == 1)
    {
        Console.WriteLine("-1");
        return;
    }
 
    // First coordinate
    int x1 = 0, y1 = 0;
 
    // Second coordinate
    int x2 = d1, y2 = 0;
 
    // Third coordinate
    int x3 = (d1 + d2 - d3) / 2;
    int y3 = (d2 + d3 - d1) / 2;
    Console.WriteLine("("+x1+", "+y1+"), ("+x2+", "+y2+") and ("+x3+", "+y3+")");
}
 
// Driver code
static void Main()
{
    int d1 = 3, d2 = 4, d3 = 5;
    solve(d1, d2, d3);
 
}
}
 
// This code is contributed by mits

Javascript




<script>
 
// Javascript implementation of the approach
 
// Function to find the original coordinated
function solve(d1, d2, d3)
{
 
    // Maximum of the given distances
    let maxx = Math.max(d1, Math.max(d2, d3));
 
    // Sum of the given distances
    let sum = (d1 + d2 + d3);
 
    // Conditions when the
    // solution doesn't exist
    if (2 * maxx > sum || sum % 2 == 1) {
        document.write("-1");
        return;
    }
 
    // First coordinate
    let x1 = 0, y1 = 0;
 
    // Second coordinate
    let x2 = d1, y2 = 0;
 
    // Third coordinate
    let x3 = parseInt((d1 + d2 - d3) / 2);
    let y3 = parseInt((d2 + d3 - d1) / 2);
    document.write("(" + x1 + ", " + y1 + "), ("
         + x2 + ", " + y2 + ") and ("
         + x3 + ", " + y3 + ")");
}
 
// Driver code
    let d1 = 3, d2 = 4, d3 = 5;
    solve(d1, d2, d3);
 
</script>
Output: 
(0, 0), (3, 0) and (1, 3)

 

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