### 600th Problem Solved

I wanted problem 600th to be a hard problem, but after few attempts, I switched back to either an easy of medium one. Turned out this one was easy. Here it is: https://leetcode.com/problems/find-positive-integer-solution-for-a-given-equation/ 1237. Find Positive Integer Solution for a Given Equation Easy 81 327 Add to List Share Given a function f(x, y) and a value z , return all positive integer pairs x and y where f(x,y) == z . The function is constantly increasing, i.e.: f(x, y) < f(x + 1, y) f(x, y) < f(x, y + 1) The function interface is defined like this: interface CustomFunction { public: // Returns positive integer f(x, y) for any given positive integer x and y. int f(int x, int y); }; For custom testing purposes you're given an integer function_id and a target z as input, where function_id represent one function from an secret internal list, on the examples you'll know only two functions from the list. You may retu