View Code of Problem 17

#include<iostream>
#include<vector>
#include<algorithm>
#include<string>

using namespace std;

int directx[4] = { 0, 1, 0, -1 };
int directy[4] = { -1, 0, 1, 0 };

int res = 0;

void dfs(vector<vector<int>>& mat, int sum, int x, int y) {

	int flag = 0;
	for (int i = 0; i < 4; i++) {

		int xx = x + directx[i];
		int yy = y + directy[i];

		if (xx < mat[0].size() && xx >= 0 && yy < mat.size() && yy >= 0) {

			if (mat[y][x] < mat[yy][xx]) {

				flag = 1;
				break;
			}	
		}
	}

	if (flag == 0) {

		res = max(res, sum);
		return;
	}

	for (int i = 0; i < 4; i++) {

		int xx = x + directx[i];
		int yy = y + directy[i];

		if (xx < mat[0].size() && xx >= 0 && yy < mat.size() && yy >= 0) {

			if (mat[y][x] < mat[yy][xx]) {

				dfs(mat, sum + 1, xx, yy);
			}
		}
	}
}

int main()
{
	int n, m;	//n行m列

	while (cin >> n >> m) {

		res = 0;
		vector<vector<int>> mat(n, vector<int>(m));
		for (int i = 0; i < n; i++) {

			for (int j = 0; j < m; j++)
				cin >> mat[i][j];
		}

		for (int i = 0; i < n; i++) {

			for (int j = 0; j < m; j++)
				dfs(mat, 0, j, i);	//每个点都选为起点尝试
		}

		cout << res << endl;
	}
}