2249. Count Lattice Points Inside a Circle

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problem

solution

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class Solution {
public:
    int countLatticePoints(vector<vector<int>>& circles) {
        set<pair<int,int>> s;
        for(vector<int> &circle: circles){
            int ox = circle[0], oy = circle[1], r = circle[2];
            int lx = ox - r;
            int rx = ox + r;
            int ly = oy - r;
            int ry = oy + r;
            for(int x = lx;x<=rx;++x){
                for(int y = ly;y<=ry ; ++y){
                    // check 
                    if(pow((x-ox),2) +pow( (y-oy),2)<=r*r){
                        s.insert({x,y});
                    }
                }
            }
        }
        return s.size();
    }
};

analysis

  • time complexity O(nxy)
  • space complexity O(1)