动态规划
class Solution {
public int maxValue(int[][] grid) {
int m = grid.length, n = grid[0].length;
int[][] dp = new int[m][n];
dp[0][0] = grid[0][0];
for(int i = 1; i < m; i++) dp[i][0] = grid[i][0] + dp[i - 1][0];
for(int i = 1; i < n; i++) dp[0][i] = grid[0][i] + dp[0][i - 1];
for(int i = 1; i < m; i++){
for(int j = 1; j < n; j++){
dp[i][j] = grid[i][j] + Math.max(dp[i - 1][j], dp[i][j - 1]);
}
}
return dp[m - 1][n - 1];
}
}