Why Does it not Working?（LC695 Max Area of Island）

LC695 Max Area of Island

class Solution {
    private int count = 0;
    public int maxAreaOfIsland(int[][] grid) {
        if(grid == null || grid.length == 0) return 0;
        int res = 0;
        
        int row = grid.length;
        int col = grid[0].length;
        for(int i = 0; i<row; i++){
            for(int j = 0; j<col; j++){
                if(grid[i][j] == 1){
                    helper(grid, i, j); //helper indicates the area expand from (i,j): int
                    res = Math.max(res, count);// and I believe the mainly mistake here is pass by value and pass by reference, in other words, temp is not changed at all
                    count = 0;
                }
            }
        }
        return res;
    }
    
    private int helper(int[][] grid, int i, int j){
        if(grid[i][j] == 1){
            grid[i][j] = 0;
            count++;
            
            if(i>0 && grid[i-1][j] == 1){ //only goes one way or maybe more way will decide whether to use if/if/if or if/else if/else if
                return helper(grid, i - 1, j);
            }
            if(i<grid.length - 1 && grid[i+1][j] == 1){
                return helper(grid, i + 1, j);
            }
            if(j>0 && grid[i][j-1] == 1){
                return helper(grid, i, j - 1);
            }
            if(j<grid[0].length - 1 && grid[i][j+1] == 1){
                return helper(grid, i, j + 1);
            } 
        }
        return 0;
    }
}

原因：不应该return helper()应该直接Helper()

class Solution {
    private int count = 0;
    public int maxAreaOfIsland(int[][] grid) {
        if(grid == null || grid.length == 0) return 0;
        int res = 0;
        
        int row = grid.length;
        int col = grid[0].length;
        for(int i = 0; i<row; i++){
            for(int j = 0; j<col; j++){
                if(grid[i][j] == 1){
                    helper(grid, i, j); //helper indicates the area expand from (i,j): int
                    res = Math.max(res, count);// and I believe the mainly mistake here is pass by value and pass by reference, in other words, temp is not changed at all
                    count = 0;
                }
            }
        }
        return res;
    }
    
    private void helper(int[][] grid, int i, int j){
        if(grid[i][j] == 1){
            grid[i][j] = 0;
            count++;
            
            if(i>0 && grid[i-1][j] == 1){ //only goes one way or maybe more way will decide whether to use if/if/if or if/else if/else if
                helper(grid, i - 1, j);
            }
            if(i<grid.length - 1 && grid[i+1][j] == 1){
                helper(grid, i + 1, j);
            }
            if(j>0 && grid[i][j-1] == 1){
                helper(grid, i, j - 1);
            }
            if(j<grid[0].length - 1 && grid[i][j+1] == 1){
                helper(grid, i, j + 1);
            } 
        }
        return;
    }
}

为什么？因为我们目的是往下走就完了（因为count是个全局变量）就往后走 一直到到最后触底return.