[leetcode]1131. 绝对值表达式的最大值 ---曼哈顿距离，四角思维

解题思路

参考这个帖子写的，下面的图片也截自这里

https://leetcode.com/problems/maximum-of-absolute-value-expression/discuss/339968/JavaC%2B%2BPython-Maximum-Manhattan-Distance

看完这个才觉得这个题跟曼哈顿距离有关系

下面的四角思维就是根据上面划线那里得出来的

我就理解了这个四角思维，还没理解这个四向思维，下面代码是八个角(没理解上面那里为什么+i,就干掉了|i-j|,有人说是因为i,？？？))


代码

class Solution {
public:
    int maxAbsValExpr(vector<int>& arr1, vector<int>& arr2) {
        vector<int>maxs(8, -INT_MAX);
        vector<int>mins(8, INT_MAX);
        int MAX = 1000000+1;
        int corner[8][3] = {{MAX,  MAX, MAX},
                            {MAX, -MAX, MAX},
                            {MAX,  MAX, MAX},
                            {MAX, -MAX, -MAX},
                            {-MAX, -MAX, -MAX},
                            {-MAX, -MAX, MAX},
                            {-MAX, MAX, -MAX},
                            {-MAX, MAX, MAX}};  //8个角落
        for(int k = 0; k < 8; k++)
        {
            for(int i = 0; i < arr1.size(); i++)
            {
                maxs[k] = max( maxs[k], abs(corner[k][0]-arr1[i]) + abs(corner[k][1] - arr2[i])+abs(corner[k][2] -i));
                mins[k] = min( mins[k], abs(corner[k][0]-arr1[i]) + abs(corner[k][1] - arr2[i])+abs(corner[k][2] -i));
            }
        }
        int res = -INT_MAX;
        for(int i = 0; i < 8; i++)
        {
            res = max(res, maxs[i]-mins[i]);
        }
        return res;
    }
};