[leetcode] 840. Magic Squares In Grid

[leetcode] 840. Magic Squares In grid

Description

A 3 x 3 magic square is a 3 x 3 grid filled with distinct numbers from 1 to 9 such that each row, column, and both diagonals all have the same sum.

Given an grid of integers, how many 3 x 3 “magic square” subgrids are there? (Each subgrid is contiguous).

Example 1:

Input: [[4,3,8,4], [9,5,1,9], [2,7,6,2]]Output: 1Explanation: The following subgrid is a 3 x 3 magic square:438951276while this one is not:384519762In total, there is only one magic square inside the given grid.

Note:

1 <= grid.length <= 101 <= grid[0].length <= 100 <= grid[i][j] <= 15

分析

题目的意思是：给你一个矩阵，找出有多少个3*3的magic squares，即对角线，横向，竖向的和都一样。 -这是我们小学的时候填数字的游戏，懂一点的都知道中间必须是5才行，然后横向，竖向，对角线的和都是15.这样编程就容易很多了，直接看代码。

代码

class Solution {public: int numMagicSquaresInside(vector>& grid) { int m=grid.size(); int n=grid[0].size(); int count=0; for(int i=0;i>& grid,int x,int y){ int pre=15; int sum=0; //each row for(int i=x;i9){ return false; } sum+=grid[i][j]; } if(pre!=sum){ return false; } } //each column for(int j=y;j

参考文献

​​840. Magic Squares In Grid​​

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