861. Score After Flipping Matrix（python+cpp）

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题目：

We have a two dimensional matrix A where each value is 0 or 1.
A move consists of choosing any row or column, and toggling each value in that row or column: changing all 0s to 1s, and all 1s to 0s.
After making any number of moves, every row of this matrix is interpreted as a binary number, and the score of the matrix is the sum of these numbers.
Return the highest possible score.
Example 1:

Input: [[0,0,1,1],
        [1,0,1,0],
        [1,1,0,0]] 
Output: 39 
Explanation: 
Toggled to [[1,1,1,1],
            [1,0,0,1],
            [1,1,1,1]]. 
0b1111 + 0b1001 + 0b1111 = 15 + 9 + 15 = 39  

Note:
1 <= A.length <= 20
1 <= A[0].length <= 20 A[i][j] is 0 or 1.

解释：
方法：
1.对于开头为0的行，进行翻转
2.对于0的数目大于1的数目的列，进行翻转
翻转可以通过与1异或实现，也可以通过用1减去实现
python代码：

class Solution(object):
    def matrixScore(self, A):
        """
        :type A: List[List[int]]
        :rtype: int
        """
         
        if not A:
            return 0
        m=len(A)
        n=len(A[0])
        def fliprow(r):
            for i in range(n):
                A[r][i]^=1
        def flipcol(c):
            for i in range(m):
                A[i][c]^=1
        #第一步，对于开头为0的行，翻转
        for i in range(m):
            if A[i][0]==0:
                fliprow(i)
        #第二步，对于0的数目大于1的数目的列，进行翻转，不处理第0列，因为经过第一步以后，第0列全是1
        #对于列进行遍历
        for i in range(1,n):
            sumofone=0
            for j in range(m):
                sumofone+=A[j][i]
            if 2*sumofone<m :
                flipcol(i)
        #求和
        _sum=0
        for i in range(m):
            _sum+=int(''.join(map(str,A[i])),2)
        return _sum

c++代码：

#inlcude<cmath>
class Solution {
public:
    int matrixScore(vector<vector<int>>& A) {
        int m=A.size();
        if(m==0)
            return 0;
        int n=A[0].size();
        //对于第一列为0的行进行翻转
        for(int i=0;i<m;i++)
            if (A[i][0]==0)
                flipr(i,A);
        //对于0的个数大于1的个数的列，翻转
        for(int i=0;i<n;i++)
        {
            int sumOne=0;
            for (int j=0;j<m;j++)
                if (A[j][i]==1)
                    sumOne++;
            if (2*sumOne<m)
                flipc(i,A);
        }
        //求和
        int _sum=0;
        for (int i=0;i<m;i++)
        {
            int base=pow(2,n-1);
            for (int j=0;j<n;j++)
            {
                 _sum+=base*A[i][j];
                base/=2;
            }   
        }
        return _sum;
    }
    void flipr(int r,vector<vector<int>>& A)
    {
        for(int i=0;i<A[0].size();i++)
            A[r][i]=1-A[r][i];
    }
    void flipc(int c,vector<vector<int>>& A)
    {
        for (int i=0;i<A.size();i++)
            A[i][c]=1-A[i][c];
    }
};

总结：