Robots Walk

/***
9.2 Imagine a robot sitting on the upper left corner of an X by Y grid. The robot can only move in two directions: 
right and down. How many possible paths are there for the robot to go from (0, 0) to (X, Y)
Follow up:
Imagine certain spots are "off limits", such that the robot cannot step on them. 
Design an algorithm to find a path for the robot from the top left to the bottom right.

IDEA: start from (X,Y), recursive until get (0, 0). each move has two options, (X-1, Y) or (X, Y-1).
***/

#include<iostream>
#include<vector>
#include <algorithm>
#include <climits>

using namespace std;

class point {
public:
    int x;
    int y;
    point(int x, int y) {
        this->x = x;
        this->y = y;
    }
};

int waysback(int x, int y) {
    if(x == 0 && y==0) return 1;
    if(x < 0 || y < 0) return 0;

    return waysback(x-1, y) + waysback(x, y-1);
}

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