840.cpp

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sample 4 ms submission
class Solution {
public:
    int numMagicSquaresInside(vector<vector<int>>& grid) {
        int m=grid.size(),n=grid[0].size(),res=0;
        for(int i=0;i<m-2;++i)
            for(int j=0;j<n-2;++j)
            {
                if(grid[i+1][j+1]==5&&isValid(grid,i,j))
                    ++res;
            }
        return res;
    }
    bool isValid(vector<vector<int>>&grid,int i,int j)
    {
        vector<int> cnt(10);
        for(int x=i;x<i+2;++x)
        {
            for(int y=j;y<j+2;++y)
            {
                int k=grid[x][y];
                if(k<1||k>9||cnt[k]==1)
                    return false;
                cnt[k]=1;
            }
        }
        if (15 != grid[i][j] + grid[i][j + 1] + grid[i][j + 2]) return false;
        if (15 != grid[i + 1][j] + grid[i + 1][j + 1] + grid[i + 1][j + 2]) return false;
        if (15 != grid[i + 2][j] + grid[i + 2][j + 1] + grid[i + 2][j + 2]) return false;
        if (15 != grid[i][j] + grid[i + 1][j] + grid[i + 2][j]) return false;
        if (15 != grid[i][j + 1] + grid[i + 1][j + 1] + grid[i + 2][j + 1]) return false;
        if (15 != grid[i][j + 2] + grid[i + 1][j + 2] + grid[i + 2][j + 2]) return false;
        if (15 != grid[i][j] + grid[i + 1][j + 1] + grid[i + 2][j + 2]) return false;
        if (15 != grid[i + 2][j] + grid[i + 1][j + 1] + grid[i][j + 2]) return false;
        return true;
    }
};
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sample 9036 kb submission
class Solution {
public:
    int numMagicSquaresInside(vector<vector<int>>& grid) {
        int res = 0;
        for(int i=1;i<grid.size()-1;++i){
            for(int j=1;j<grid[i].size()-1;++j){
                if(grid[i][j]==5){
                    if(isMagic(grid,i,j)) res++;
                }
            }
        }
        return res;
    }
private:
    int data[16] = {43816729, 38167294, 81672943, 16729438, 67294381, 72943816, 29438167, 94381672,27618349, 76183492, 61834927, 18349276, 83492761, 34927618, 49276183, 92761834};
    bool isMagic(vector<vector<int>>& grid, int i, int j){
        int cmp = grid[i-1][j-1];
        cmp = cmp*10+grid[i-1][j];
        cmp = cmp*10+grid[i-1][j+1];
        cmp = cmp*10+grid[i][j+1];
        cmp = cmp*10+grid[i+1][j+1];
        cmp = cmp*10+grid[i+1][j];
        cmp = cmp*10+grid[i+1][j-1];
        cmp = cmp*10+grid[i][j-1];
        //printf("%d\n",cmp);
        for(int i=0;i<16;i++){
            if(data[i]==cmp) return true;
        }
        return false;
    }
};
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