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本帖最后由 798236606 于 2020-3-5 10:12 编辑
传送门:https://leetcode-cn.com/problems/rotting-oranges/
BFS
- class Solution {
- public:
- struct Pos{
- int x, y;
- };
- int good = 0;
- bool vis[15][15] = {false};
- queue<Pos> q;
- void turn_bad(int x, int y)
- {
- q.push({x, y});
- vis[x][y] = true;
- --good;
- }
- int orangesRotting(vector<vector<int>>& grid) {
- int r = grid.size(), c = grid[0].size();
- for (int i = 0; i < r; ++i)
- {
- for (int j = 0; j < c; ++j)
- {
- if (grid[i][j] == 2)
- {
- q.push({i, j});
- vis[i][j] = true;
- }
- if (grid[i][j] == 1) ++good;
- }
- }
- if (!good) return 0;
- int t = 0;
- while (int k = q.size())
- {
- if (!good) return t;
- while (k--)
- {
- Pos p = q.front();
- q.pop();
- if (p.x > 0 && !vis[p.x - 1][p.y] && grid[p.x - 1][p.y] == 1) turn_bad(p.x - 1, p.y);
- if (p.x < r - 1 && !vis[p.x + 1][p.y] && grid[p.x + 1][p.y] == 1) turn_bad(p.x + 1, p.y);
- if (p.y > 0 && !vis[p.x][p.y - 1] && grid[p.x][p.y - 1] == 1) turn_bad(p.x, p.y - 1);
- if (p.y < c - 1 && !vis[p.x][p.y + 1] && grid[p.x][p.y + 1] == 1) turn_bad(p.x, p.y + 1);
- }
- ++t;
- }
- return -1;
- }
- };
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