leetcode 361.Bomb Enemy(lintcode 553. Bomb Enemy)

dp

分别计算从左到右、从右到左、从上到下、从下到上4个方向可能的值，然后计算所有为‘0’的地方的4个方向的值的最大值

https://www.cnblogs.com/grandyang/p/5599289.html

class Solution {
public:
    /**
     * @param grid: Given a 2D grid, each cell is either 'W', 'E' or '0'
     * @return: an integer, the maximum enemies you can kill using one bomb
     */
    int maxKilledEnemies(vector<vector<char> > &grid) {
        // write your code here
        int m = grid.size();
        if(m <= )
            return ;
        int n = grid[].size();
        if(n <= )
            return ;
        vector<vector<int> > left(m,vector<int>(n,)),right(m,vector<int>(n,)),top(m,vector<int>(n,)),down(m,vector<int>(n,));
        for(int i = ;i < m;i++){
            for(int j = ;j < n;j++){
                int tmp;
                if(j ==  || grid[i][j] == 'W')
                    tmp = ;
                else
                    tmp = left[i][j-];
                if(grid[i][j] == 'E')
                    left[i][j] = tmp + ;
                else
                    left[i][j] = tmp;
            }
        }
        for(int i = ;i < m;i++){
            for(int j = n - ;j >= ;j--){
                int tmp;
                if(j == n -  || grid[i][j] == 'W')
                    tmp = ;
                else
                    tmp = right[i][j+];
                if(grid[i][j] == 'E')
                    right[i][j] = tmp + ;
                else
                    right[i][j] = tmp;
            }
        }
        for(int j = ;j < n;j++){
            for(int i = ;i < m;i++){
                int tmp;
                if(i ==  || grid[i][j] == 'W')
                    tmp = ;
                else
                    tmp = top[i-][j];
                if(grid[i][j] == 'E')
                    top[i][j] = tmp + ;
                else
                    top[i][j] = tmp;
            }
        }
        for(int j = ;j < n;j++){
            for(int i = m-;i >= ;i--){
                int tmp;
                if(i == m- || grid[i][j] == 'W')
                    tmp = ;
                else
                    tmp = down[i+][j];
                if(grid[i][j] == 'E')
                    down[i][j] = tmp + ;
                else
                    down[i][j] = tmp;
            }
        }
        int max_num = ;
        for(int i = ;i < m;i++){
            for(int j = ;j < n;j++){
                if(grid[i][j] == '')
                    max_num = max(max_num,left[i][j] + right[i][j] + top[i][j] + down[i][j]);
            }
        }
        return max_num;
    }
};