576. 出界的路径数

class Solution {
    int MOD=(int)1e9+7;
    Long memo[][][];
    public int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
        /**
        记忆化dfs
         */
         memo=new Long[m][n][maxMove+1];
        return (int)dfs(m,n,maxMove,startRow,startColumn);
         
    }

    public long dfs(int m, int n, int maxMove, int i, int j){
        if(i<0||j<0||i>=m||j>=n){
            return 1;
        }
        if(maxMove==0){
            return 0;
        }
        if(memo[i][j][maxMove]!=null){
            return memo[i][j][maxMove];
        }
        long  res=0;
        res=(res+dfs(m,n,maxMove-1,i-1,j))%MOD;
        res=(res+dfs(m,n,maxMove-1,i+1,j))%MOD;
        res=(res+dfs(m,n,maxMove-1,i,j-1))%MOD;
        res=(res+dfs(m,n,maxMove-1,i,j+1))%MOD;
        memo[i][j][maxMove]=res;
        return res;
    }
}