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Check if two people starting from different points ever meet
• Difficulty Level : Easy
• Last Updated : 05 May, 2021

There are two people that start from two different positions, let’s say x1 and x2. Both can jump v1 and v2 meters ahead respectively. We have to find if both will ever meet given that the number of jumps taken by both has to be same.
Print ‘Yes’ if they will meet,
print ‘No’ they will not.

Examples :

```Input  : x1 = 5, v1 = 8, x2 = 4, v2 = 7
Output : No
Explanation: The first person is starting ahead of the second one.
and his speed is also greater than the second one, so they will never meet.

Input  : x1 = 6, v1 = 6, x2 = 4, v2 = 8
Output : Yes```

Naive Approach: In this, we calculate the position of each person after each jump and checks if they have landed in the same spot or not. This one having complexity O(n).

## C++

 `// C++ program to find if two people``// starting from different positions``// ever meet or not.``#include ``using` `namespace` `std;` `bool` `everMeet(``int` `x1, ``int` `x2, ``int` `v1, ``int` `v2)``{``    ``// If speed of a person at a position before``    ``// other person is smaller, then return false.``    ``if` `(x1 < x2 && v1 <= v2)``       ``return` `false``;``    ``if` `(x1 > x2 && v1 >=v2)``       ``return` `false``; ``  ` `    ``// Making sure that x1 is greater``    ``if` `(x1 < x2)``    ``{``        ``swap(x1, x2);``        ``swap(v1, v2);``    ``}    ``  ` `     ``// Until one person crosses other``     ``while` `(x1 >= x2) {``        ``if` `(x1 == x2)``            ``return` `true``;``        ` `        ``// first person taking one``        ``// jump in each iteration``        ``x1 = x1 + v1;``        ` `        ``// second person taking``        ``// one jump in each iteration``        ``x2 = x2 + v2;``    ``}` `    ``return` `false``;  ``}` `// Driver code``int` `main()``{``    ``int` `x1 = 5, v1 = 8, x2 = 4, v2 = 7;``    ``if` `(everMeet(x1, x2, v1, v2))``        ``printf``(``"Yes"``);   ``    ``else``        ``printf``(``"No"``);``    ``return` `0;``}`

## Java

 `// Java program to find``// if two people starting``// from different positions``// ever meet or not.``import` `java.io.*;` `class` `GFG``{``    ``static` `void` `swap(``int` `a, ``int` `b)``    ``{``        ``int` `t = a;``        ``a = b;``        ``b = t;``    ``}``    ``static` `boolean` `everMeet(``int` `x1, ``int` `x2,``                            ``int` `v1, ``int` `v2)``    ``{``        ``// If speed of a person``        ``// at a position before``        ``// other person is smaller,``        ``// then return false.``        ``if` `(x1 < x2 && v1 <= v2)``        ``return` `false``;``        ``if` `(x1 > x2 && v1 >= v2)``        ``return` `false``;``        ` `        ``// Making sure that``        ``// x1 is greater``        ``if` `(x1 < x2)``        ``{``            ``swap(x1, x2);``            ``swap(v1, v2);``        ``}``    ` `        ``// Until one person``        ``// crosses other``        ``while` `(x1 >= x2)``        ``{``            ``if` `(x1 == x2)``                ``return` `true``;``            ` `            ``// first person taking one``            ``// jump in each iteration``            ``x1 = x1 + v1;``            ` `            ``// second person taking``            ``// one jump in each iteration``            ``x2 = x2 + v2;``        ``}``    ` `        ``return` `false``;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `x1 = ``5``, v1 = ``8``,``            ``x2 = ``4``, v2 = ``7``;``        ``if` `(everMeet(x1, x2, v1, v2))``            ``System.out.println(``"Yes"``);``        ``else``            ``System.out.println(``"No"``);``    ``}``}` `// This code is contributed``// by akt_mit`

## Python3

 `# Python3 program to find if two``# people starting from different``# positions ever meet or not.` `def` `everMeet(x1, x2, v1, v2):` `    ``# If speed of a person at``    ``# a position before other``    ``# person is smaller, then``    ``# return false.``    ``if` `(x1 < x2 ``and` `v1 <``=` `v2):``        ``return` `False``;``    ``if` `(x1 > x2 ``and` `v1 >``=` `v2):``        ``return` `False``;` `    ``# Making sure that``    ``# x1 is greater``    ``if` `(x1 < x2):` `        ``x1, x2 ``=` `x2,x1;``        ``v1, v2 ``=` `v2,v1;``    `  `    ``# Until one person``    ``# crosses other``    ``while` `(x1 >``=` `x2):``    ` `        ``if` `(x1 ``=``=` `x2):``            ``return` `True``;``        ` `        ``# first person taking one``        ``# jump in each iteration``        ``x1 ``=` `x1 ``+` `v1;``        ` `        ``# second person taking``        ``# one jump in each iteration``        ``x2 ``=` `x2 ``+` `v2;``    `  `    ``return` `False``;`  `# Driver code``x1 ``=` `5``;``v1 ``=` `8``;``x2 ``=` `4``;``v2 ``=` `7``;``if` `(everMeet(x1, x2,v1, v2)):``    ``print``(``"Yes"``);``else``:``    ``print``(``"No"``);` `# This code is contributed by mits`

## C#

 `// C# program to find if two``// people starting from different``// positions ever meet or not.``using` `System;` `class` `GFG``{``    ``static` `void` `swap(``ref` `int` `a,``                     ``ref` `int` `b)``    ``{``        ``int` `t = a;``        ``a = b;``        ``b = t;``    ``}``    ``static` `bool` `everMeet(``int` `x1, ``int` `x2,``                         ``int` `v1, ``int` `v2)``    ``{``        ``// If speed of a person at a``        ``// position before other person``        ``// is smaller, then return false.``        ``if` `(x1 < x2 && v1 <= v2)``        ``return` `false``;``        ``if` `(x1 > x2 && v1 >= v2)``        ``return` `false``;``        ` `        ``// Making sure that x1 is greater``        ``if` `(x1 < x2)``        ``{``            ``swap(``ref` `x1, ``ref` `x2);``            ``swap(``ref` `v1, ``ref` `v2);``        ``}``    ` `        ``// Until one person crosses other``        ``while` `(x1 >= x2)``        ``{``            ``if` `(x1 == x2)``                ``return` `true``;``            ` `            ``// first person taking one``            ``// jump in each iteration``            ``x1 = x1 + v1;``            ` `            ``// second person taking``            ``// one jump in each iteration``            ``x2 = x2 + v2;``        ``}``    ` `        ``return` `false``;``    ``}``    ` `    ``// Driver code``    ``static` `void` `Main()``    ``{``        ``int` `x1 = 5, v1 = 8,``            ``x2 = 4, v2 = 7;``        ``if` `(everMeet(x1, x2, v1, v2))``            ``Console.Write(``"Yes"``);``        ``else``            ``Console.Write(``"No"``);``    ``}``}` `// This code is contributed by``// Manish Shaw(manishshaw1)`

## PHP

 ` ``\$x2` `&& ``\$v1` `>= ``\$v2``)``        ``return` `false;` `    ``// Making sure that``    ``// x1 is greater``    ``if` `(``\$x1` `< ``\$x2``)``    ``{``        ``list(``\$x1``, ``\$x2``) = ``array``(``\$x2``,``                               ``\$x1``);``        ``list(``\$v1``, ``\$v2``) = ``array``(``\$v2``,``                               ``\$v1``);``    ` `    ``}` `    ``// Until one person``    ``// crosses other``    ``while` `(``\$x1` `>= ``\$x2``)``    ``{``        ``if` `(``\$x1` `== ``\$x2``)``            ``return` `true;``        ` `        ``// first person taking one``        ``// jump in each iteration``        ``\$x1` `= ``\$x1` `+ ``\$v1``;``        ` `        ``// second person taking``        ``// one jump in each iteration``        ``\$x2` `= ``\$x2` `+ ``\$v2``;``    ``}` `    ``return` `false;``}` `// Driver code``\$x1` `= 5;``\$v1` `= 8;``\$x2` `= 4;``\$v2` `= 7;``if` `(everMeet(``\$x1``, ``\$x2``,``             ``\$v1``, ``\$v2``))``    ``echo` `"Yes"``;``else``    ``echo` `"No"``;` `// This code is contributed by ajit``?>`

## Javascript

 ``
Output:
`No`

Efficient approach: Other way is to use the concept of Relative Speed. If the X1 is D distance away from X2, then relative speed of X1 should be in factors of D so as both land on the same spot.
Example:
X1 = 10
X2 = 25
V1 = 10
V2 = 8
Since here D = 15 and relative speed = 2 which is not a factor of D they will never meet.
The time complexity of this algorithm is O(1)

Imlementation is given below:

## C++

 `// C++ program to find if two people``// starting from different positions``// ever meet or not.``#include ``using` `namespace` `std;` `bool` `everMeet(``int` `x1, ``int` `x2, ``int` `v1, ``int` `v2)``{` `    ``// If speed of a person at a position before``    ``// other person is smaller, then return false.``    ``if` `(x1 < x2 && v1 <= v2)``       ``return` `false``;``    ``if` `(x1 > x2 && v1 >= v2)``       ``return` `false``; ` `    ``// Making sure that x1 is greater``    ``if` `(x1 < x2)``    ``{``        ``swap(x1, x2);``        ``swap(v1, v2);``    ``}   ` `    ``// checking if relative speed is``    ``// a factor of relative distance or not``    ``return` `((x1 - x2) % (v1 - v2) == 0);``}` `// Driver code``int` `main()``{``    ``int` `x1 = 5, v1 = 8, x2 = 4, v2 = 7;``    ``if` `(everMeet(x1, x2, v1, v2))``        ``printf``(``"Yes"``);   ``    ``else``        ``printf``(``"No"``);``    ``return` `0;``}`

## Java

 `// Java program to find if two people``// starting from different positions``// ever meet or not.` `public` `class` `GFG {` `    ``static` `boolean` `everMeet(``int` `x1, ``int` `x2, ``int` `v1, ``int` `v2) {` `        ``// If speed of a person at a position before``        ``// other person is smaller, then return false.``        ``if` `(x1 < x2 && v1 <= v2) {``            ``return` `false``;``        ``}``        ``if` `(x1 > x2 && v1 >= v2) {``            ``return` `false``;``        ``}` `        ``// Making sure that x1 is greater``        ``if` `(x1 < x2) {``            ``swap(x1, x2);``            ``swap(v1, v2);``        ``}` `        ``// checking if relative speed is``        ``// a factor of relative distance or not``        ``return` `((x1 - x2) % (v1 - v2) == ``0``);``    ``}` `    ``static` `void` `swap(``int` `a, ``int` `b) {``        ``int` `t = a;``        ``a = b;``        ``b = t;``    ``}` `    ``public` `static` `void` `main(String[] args) {``        ``int` `x1 = ``5``, v1 = ``8``, x2 = ``4``, v2 = ``7``;``        ``if` `(everMeet(x1, x2, v1, v2)) {``            ``System.out.printf(``"Yes"``);``        ``} ``else` `{``            ``System.out.printf(``"No"``);``        ``}``    ``}``}` `// This code is contributed by 29AjayKumar`

## Python3

 `    ` `# Python3 program to find if two people``# starting from different positions``# ever meet or not.` `def` `everMeet(x1, x2, v1, v2):` `    ``# If speed of a person at a position before``    ``# other person is smaller, then return false.``    ``if` `(x1 < x2 ``and` `v1 <``=` `v2):``        ``return` `False``;``        ``if` `(x1 > x2 ``and` `v1 >``=` `v2):``            ``return` `False``;``            ` `            ``# Making sure that x1 is greater``            ``if` `(x1 < x2):``                ``swap(x1, x2)``                ``swap(v1, v2)``                ` `                ``# checking if relative speed is``                ``# a factor of relative distance or not``                ``return` `((x1 ``-` `x2) ``%` `(v1 ``-` `v2) ``=``=` `0``)``                ``def` `swap(a, b):``                    ``t ``=` `a``                    ``a ``=` `b``                    ``b ``=` `t``# Driver code``def` `main():``    ` `    ``x1, v1, x2, v2 ``=``5``, ``8``, ``4``, ``7``    ``if` `(everMeet(x1, x2, v1, v2)):``        ``print``(``"Yes"``)``    ``else``:``        ``print``(``"No"``)` `if` `__name__ ``=``=` `'__main__'``:``    ``main()``    ` `    ` `# This code is contributed by 29AjayKumar`

## C#

 `//C# program to find if two people``// starting from different positions``// ever meet or not.``using` `System;``public` `class` `GFG{`  `    ``static` `bool` `everMeet(``int` `x1, ``int` `x2, ``int` `v1, ``int` `v2) {` `        ``// If speed of a person at a position before``        ``// other person is smaller, then return false.``        ``if` `(x1 < x2 && v1 <= v2) {``            ``return` `false``;``        ``}``        ``if` `(x1 > x2 && v1 >= v2) {``            ``return` `false``;``        ``}` `        ``// Making sure that x1 is greater``        ``if` `(x1 < x2) {``            ``swap(x1, x2);``            ``swap(v1, v2);``        ``}` `        ``// checking if relative speed is``        ``// a factor of relative distance or not``        ``return` `((x1 - x2) % (v1 - v2) == 0);``    ``}` `    ``static` `void` `swap(``int` `a, ``int` `b) {``        ``int` `t = a;``        ``a = b;``        ``b = t;``    ``}` `    ``public` `static` `void` `Main() {``        ``int` `x1 = 5, v1 = 8, x2 = 4, v2 = 7;``        ``if` `(everMeet(x1, x2, v1, v2)) {``            ``Console.WriteLine(``"Yes"``);``        ``} ``else` `{``            ``Console.WriteLine(``"No"``);``        ``}``    ``}``}`  `// This code is contributed by 29AjayKumar`

## PHP

 ` ``\$x2` `&& ``\$v1` `>= ``\$v2``)``        ``return` `false;` `    ``// Making sure that x1 is greater``    ``if` `(``\$x1` `< ``\$x2``)``    ``{``        ``list(``\$x1``, ``\$x2``) = ``array``(``\$x2``, ``\$x1``);``        ``list(``\$v2``, ``\$v1``) = ``array``(``\$v1``, ``\$v2``);``    ``}` `    ``// checking if relative speed is``    ``// a factor of relative distance or not``    ``return` `((``\$x1` `- ``\$x2``) % (``\$v1` `- ``\$v2``) == 0);``}` `// Driver code``\$x1` `= 5; ``\$v1` `= 8;``\$x2` `= 4; ``\$v2` `= 7;``if` `(everMeet(``\$x1``, ``\$x2``, ``\$v1``, ``\$v2``))``    ``print``(``"Yes"``);``else``    ``print``(``"No"``);` `// This code is contributed by mits``?>`

## Javascript

 ``
Output :
`No`

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