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Commit 3a3b293

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Merge pull request #324 from Hardvan/rotten-oranges
Add Rotten Oranges Graph Problem using BFS
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‎README.md‎

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</a>
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</td>
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</tr>
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<tr>
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<td>Rotten Oranges</td>
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<td> <!-- C -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- C++ -->
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<a href="./src/cpp/RottenOranges.cpp">
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<img align="center" height="25" src="./logos/cplusplus.svg" />
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</a>
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</td>
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<td> <!-- Java -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Python -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Go -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Ruby -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- JavaScript -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Swift -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Rust -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Scala -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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<td> <!-- Kotlin -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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</a>
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</td>
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</tr>
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<td>Isogram</td>
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<td> <!-- C -->

‎src/cpp/RottenOranges.cpp‎

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#include <bits/stdc++.h>
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using namespace std;
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/*
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Problem Statement:
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Given an m x n grid, where each cell has the following values:
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2 – Rotten orange
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1 – Fresh orange
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0 – Empty cell
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Every minute, if a Fresh orange is adjacent to a Rotten Orange in 4-direction
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(upward, downwards, right, and left) it becomes Rotten.
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Return the minimum number of minutes required such that
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none of the cells has a Fresh Orange.
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If it's not possible, return -1.
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*/
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// Approach: BFS
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bool isValid(int nx, int ny, int m, int n)
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{
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return (0 <= nx && nx < m) &&
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(0 <= ny && ny < n);
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}
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// Time: O(mn) x 4
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// Space: O(mn)
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int orangesRotting(vector<vector<int>> &grid)
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{
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int m = grid.size();
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int n = grid[0].size();
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int total = 0; // fresh + rotten oranges
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int count = 0; // rotten oranges
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int mins = 0; // minutes elapsed
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queue<pair<int, int>> rotten; // {i, j}: position of rotten orange
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// Count the fresh & rotten oranges, push rotten oranges into queue
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for (int i = 0; i < m; i++)
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{
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for (int j = 0; j < n; j++)
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{
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if (grid[i][j] != 0) // Rotten or Fresh orange
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total++;
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if (grid[i][j] == 2) // Rotten
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rotten.push({i, j}); // Push position of rotten orange
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}
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}
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int dx[] = {0, 0, -1, 1}; // 4-directions (x-axis)
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int dy[] = {-1, 1, 0, 0}; // 4-directions (y-axis)
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while (!rotten.empty())
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{
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int size = rotten.size(); // rotten oranges in current minute
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count += size; // add to total rotten oranges
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while (size--) // Each rotten orange in current minute
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{
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// Pop the front rotten orange
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int x = rotten.front().first;
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int y = rotten.front().second;
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rotten.pop();
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// Check for fresh oranges in 4-directions
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for (int i = 0; i < 4; i++)
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{
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// New coordinates
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int nx = x + dx[i];
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int ny = y + dy[i];
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// Valid, fresh orange
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if (isValid(nx, ny, m, n) && grid[nx][ny] == 1)
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{
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grid[nx][ny] = 2; // make it rotten
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rotten.push({nx, ny}); // push it into queue
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}
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}
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}
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if (!rotten.empty()) // if there are more rotten oranges
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mins++;
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}
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if (total != count) // fresh oranges left
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return -1;
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return mins;
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}
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int main()
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{
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vector<vector<int>> grid = {{2, 1, 1},
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{1, 1, 0},
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{0, 1, 1}};
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cout << orangesRotting(grid) << endl; // 4
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return 0;
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}

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