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| 1 | +// Source : https://leetcode.com/problems/rotting-oranges/ |
| 2 | +// Author : David Lin |
| 3 | +// Date : 2023-05-18 |
| 4 | + |
| 5 | +/********************************************************************************** |
| 6 | + * |
| 7 | +You are given an m x n grid where each cell can have one of three values: |
| 8 | +
|
| 9 | +0 representing an empty cell, |
| 10 | +1 representing a fresh orange, or |
| 11 | +2 representing a rotten orange. |
| 12 | +Every minute, any fresh orange that is 4-directionally adjacent to a rotten orange becomes rotten. |
| 13 | +
|
| 14 | +Return the minimum number of minutes that must elapse until no cell has a fresh orange. If this is impossible, return -1. |
| 15 | + * |
| 16 | + * Example 1: |
| 17 | + * 211 |
| 18 | + * 110 |
| 19 | + * 011 |
| 20 | + * Answer: 4 |
| 21 | + * |
| 22 | + * Example 2: |
| 23 | + * 211 |
| 24 | + * 011 |
| 25 | + * 101 |
| 26 | + * Answer: -1 |
| 27 | + * |
| 28 | + * Example 3: |
| 29 | + * 02 |
| 30 | + * Answer: 0 |
| 31 | + * |
| 32 | + * |
| 33 | + * |
| 34 | + **********************************************************************************/ |
| 35 | + |
| 36 | +#include <iostream> |
| 37 | +#include <vector> |
| 38 | +#include <queue> |
| 39 | +#include <stack> |
| 40 | + |
| 41 | +using namespace std; |
| 42 | + |
| 43 | + |
| 44 | +int orangesRotting(vector<vector<int> >& grid) { |
| 45 | + int minutes{}; |
| 46 | + int num_fresh{}; |
| 47 | + queue<pair<int, int>> q; |
| 48 | + int row_size = grid.size(); |
| 49 | + int col_size = grid[0].size(); |
| 50 | + for(int row{}; row < row_size; row++){ |
| 51 | + for(int col{}; col< col_size; col++){ |
| 52 | + switch (grid[row][col]) |
| 53 | + { |
| 54 | + case 2: |
| 55 | + q.push({row, col}); |
| 56 | + break; |
| 57 | + case 1: |
| 58 | + num_fresh++; |
| 59 | + break; |
| 60 | + default: |
| 61 | + break; |
| 62 | + } |
| 63 | + } |
| 64 | + } |
| 65 | + |
| 66 | + vector<pair<int, int>> directions = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}}; |
| 67 | + int q_size = q.size(); |
| 68 | + if (q_size == 0){ |
| 69 | + if (num_fresh == 0)return 0; |
| 70 | + return -1; |
| 71 | + } |
| 72 | + |
| 73 | + while (!q.empty()) |
| 74 | + { |
| 75 | + if(q_size == 0 && q.size() > 0){ |
| 76 | + minutes++; |
| 77 | + q_size = q.size(); |
| 78 | + } |
| 79 | + int row = q.front().first; |
| 80 | + int col = q.front().second; |
| 81 | + q.pop(); |
| 82 | + |
| 83 | + for(auto& direction: directions){ |
| 84 | + int new_row = row + direction.first; |
| 85 | + int new_col = col + direction.second; |
| 86 | + if(new_row < row_size && new_row >= 0 && new_col < col_size && new_col >= 0){ |
| 87 | + if(grid[new_row][new_col] == 1){ |
| 88 | + grid[new_row][new_col] = 2; |
| 89 | + q.push({new_row, new_col}); |
| 90 | + num_fresh--; |
| 91 | + } |
| 92 | + } |
| 93 | + } |
| 94 | + q_size--; |
| 95 | + } |
| 96 | + if(num_fresh > 0)return -1; |
| 97 | + return minutes; |
| 98 | +} |
| 99 | + |
| 100 | + |
| 101 | +int main(void) |
| 102 | +{ |
| 103 | + vector< vector<int> > grid; |
| 104 | + grid.push_back( vector<int>(1, 0) ); |
| 105 | + cout << orangesRotting(grid) << endl; |
| 106 | + grid.clear(); |
| 107 | + |
| 108 | + grid = {{2,1,1},{1,1,0},{0,1,1}}; |
| 109 | + cout << orangesRotting(grid) << endl; |
| 110 | + grid.clear(); |
| 111 | + |
| 112 | + grid = {{2,1,1},{0,1,1},{1,0,1}}; |
| 113 | + cout << orangesRotting(grid) << endl; |
| 114 | + grid.clear(); |
| 115 | + |
| 116 | + grid = {{0,2}}; |
| 117 | + cout << orangesRotting(grid) << endl; |
| 118 | + return 0; |
| 119 | +} |
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