Sword finger offer 47 Maximum value of gifts

The finger of the sword Offer 47. The greatest value of gifts

class Solution {
    
    public int maxValue(int[][] grid) {
    
        int n = grid[0].length, m = grid.length; 
        int[][] dp = new int[m][n];
        dp[0][0] = grid[0][0];

        for(int i = 1; i < n ; i++){
    
            dp[0][i] += dp[0][i-1] + grid[0][i];
        }
        for(int i = 1; i < m ; i++){
    
            dp[i][0] += dp[i-1][0] + grid[i][0];
        }
        for(int i = 1; i < m; i++){
     //  Start with the second line 
            for(int j = 1; j < n; j++){
     //  From the second column  
                dp[i][j] = Math.max(dp[i][j-1], dp[i-1][j]) + grid[i][j];
            }
        }
        return dp[m-1][n-1];
    }
}

class Solution {
    
    public int maxValue(int[][] grid) {
    
        int n = grid[0].length, m = grid.length; //  Number of columns 
        int[] arr = grid[0]; //  First line prefix and 
        for(int i = 1; i < n ; i++){
    
            arr[i] += arr[i-1];
        }
        for(int i = 1; i < m; i++){
     //  Start with the second line 
            arr[0] += grid[i][0];
            for(int j = 1; j < n; j++){
     //  From the second column 
                // arr[j] = Math.max(arr[j], arr[j-1]) + grid[i][j];
                arr[j] = (arr[j] > arr[j-1] ? arr[j] : arr[j-1]) + grid[i][j];
            }
        }
        return arr[n-1];
    }
}