807.保持城市天际线.md

方法一：贪心。

这道题的思想就是找出每行、每列的最大值，然后取两者的最小值作为每个单元格上的值，求差

class Solution {
    public int maxIncreaseKeepingSkyline(int[][] grid) {
        int rows = grid.length;
        if (rows == 0) return 0;
        int cols = grid[0].length;
        int[] linemax = new int[rows];
        int[] colmax = new int[cols];
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                linemax[i] = Math.max(linemax[i], grid[i][j]);
                colmax[j] = Math.max(colmax[j], grid[i][j]);
            }
        }
        int res = 0;
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                res += (Math.min(linemax[i], colmax[j]) - grid[i][j]);
                grid[i][j] = Math.min(linemax[i], colmax[j]);
            }
        }
        return res;
    }
}