LeetCode Daily Problem P2257 Count Unguarded Cells in the Grid

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Timeline

Timeline

2025-11-02

init

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Problem:

P2257 Count Unguarded Cells in the Grid

https://leetcode.cn/problems/count-unguarded-cells-in-the-grid/description/?envType=daily-question&envId=2025-11-02

#include <vector>
using std::vector;

class Solution {
    public:
	int countUnguarded(int m, int n, vector<vector<int> > &guards,
			   vector<vector<int> > &walls)
	{
		// 0 as not protected, 1 as protected, 2 as guards, 3 as walls
		// inital as not protected(0)
		vector<vector<int> > grid_map(m, vector<int>(n, 0));
		int i, j;
		int len;
		int g_i, g_j;
		int count = 0;

		len = walls.size();
		for (i = 0; i < len; i++) {
			grid_map[walls[i][0]][walls[i][1]] = 3;
		}

		len = guards.size();
		for (i = 0; i < len; i++) {
			grid_map[guards[i][0]][guards[i][1]] = 2;
		}

		for (i = 0; i < len; i++) {
			// guards[i][0], guards[i][1]
			g_i = guards[i][0];
			g_j = guards[i][1];
			// Up
			j = 1;
			while (g_i - j >= 0) {
				if (grid_map[g_i - j][g_j] == 2 ||
				    grid_map[g_i - j][g_j] == 3) {
					break;
				}
				grid_map[g_i - j][g_j] = 1;
				j++;
			}

			// Down
			j = 1;
			while (g_i + j < m) {
				if (grid_map[g_i + j][g_j] == 2 ||
				    grid_map[g_i + j][g_j] == 3) {
					break;
				}
				grid_map[g_i + j][g_j] = 1;
				j++;
			}

			// Left
			j = 1;
			while (g_j - j >= 0) {
				if (grid_map[g_i][g_j - j] == 2 ||
				    grid_map[g_i][g_j - j] == 3) {
					break;
				}
				grid_map[g_i][g_j - j] = 1;
				j++;
			}
			// Right
			j = 1;
			while (g_j + j < n) {
				if (grid_map[g_i][g_j + j] == 2 ||
				    grid_map[g_i][g_j + j] == 3) {
					break;
				}
				grid_map[g_i][g_j + j] = 1;
				j++;
			}
		}
		for (i = 0; i < m; i++) {
			for (j = 0; j < n; j++) {
				if (grid_map[i][j] == 0) {
					count++;
				}
			}
		}
		return count;
	}
};

#include <stdio.h>
int main()
{
	vector<vector<int> > guards = { { 0, 0 }, { 1, 1 }, { 2, 3 } };
	vector<vector<int> > walls = { { 0, 1 }, { 2, 2 }, { 1, 4 } };
	int m=4, n=6;
	Solution s;
	printf("%d\n",s.countUnguarded(m, n, guards, walls));
}