360公司 2020秋招 技术综合B卷 ，表面积问题

当时在线写时碰到了定义二维数组时使用  vector<vector<int>> arr，但是在cin >> arr[i][j]; 会出现错误，超出范围的问题，不晓得怎么解决，然后百度后使用了现在定义二维数组的方法，

int **arr;
arr = new int *[N];
for (int i = 0; i < N; i++)
	arr[i] = new int[M];

 

#include<iostream>
using namespace std;
#include<vector>;

int N, M;  int S_L = 0, S_R = 0, S_F = 0, S_B = 0,S=0; //vector<vector<int>> arr;
int main()
{
	cin >> N >> M;
	
	//生成二维数组
	int **arr;
	arr = new int *[N];
	for (int i = 0; i < N; i++)
		arr[i] = new int[M];

	for (int i = 0; i < N; i++)
	{
		for (int j = 0; j < M; j++)
			cin >> arr[i][j];

	}

	if (N >= 1 && M <= 1000)
	{
	  
		for (int i = 0; i < N; i++)
		{
			for (int j = 0; j < M; j++)
			{
				//当前方块左边的表面积	
				if (j - 1 < 0)
					S_L += arr[i][j];
				else
				{
					if (arr[i][j] - arr[i][j - 1] > 0)
					{
						S_L = S_L + arr[i][j] - arr[i][j - 1];
					}					
				}
				//当前方块右边的表面积
				if (j + 1 >= M)
					S_R += arr[i][j];
				else
				{
					if(arr[i][j]-arr[i][j+1]>0)
						S_R = S_R + arr[i][j] - arr[i][j + 1];
				}
				//当前块前面的表面积
				if (i + 1 >= N)
					S_F += arr[i][j];
				else
				{
					if (arr[i][j] - arr[i + 1][j] > 0)
						S_F = S_F + arr[i][j] - arr[i + 1][j];
				}
				//当前块后面的表面积

				if (i - 1 < 0)
					S_B += arr[i][j];
				else
				{
					if (arr[i][j] - arr[i - 1][j] > 0)
						S_B = S_B + arr[i][j] - arr[i - 1][j];
				}
				
			}
		}
		S = S_B + S_F + S_L + S_R + 2 * N*M; //N*M为上下两个面的面积
		cout << S<< endl;

	}
	system("pause");
	return 0;
}