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Commit 06be5bd

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solves number of islands in java
1 parent 97f179c commit 06be5bd

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2 files changed

+53
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+53
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‎README.md

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| 191 | [Number of One Bits](https://leetcode.com/problems/number-of-1-bits) | [![Java](assets/java.png)](src/NumberOf1Bit.java) [![Python](assets/python.png)](python/number_of_1_bits.py) | |
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| 198 | [House Robber](https://leetcode.com/problems/house-robber) | [![Java](assets/java.png)](src/HouseRobber.java) [![Python](assets/python.png)](python/house_robber.py) | |
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| 199 | [Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view) | [![Java](assets/java.png)](src/BinaryTreeRightSideView.java) | |
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| 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands) | | |
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| 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands) | [![Java](assets/java.png)](src/NumberOfIslands.java) | |
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| 201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range) | | |
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| 202 | [Happy Number](https://leetcode.com/problems/happy-number) | [![Java](assets/java.png)](src/HappyNumber.java) [![Python](assets/python.png)](python/happy_number.py) | |
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| 203 | [Remove Linked List Elements](https://leetcode.com/problems/remove-linked-list-elements) | [![Java](assets/java.png)](src/RemoveLinkedListElements.java) [![Python](assets/python.png)](python/remove_linked_list_elements.py) | |

‎src/NumberOfIslands.java

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// https://leetcode.com/problems/number-of-islands
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// T: O(m * n)
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// T: O(m * n)
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public class NumberOfIslands {
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private static final char VISITED = '0';
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private static final char ISLAND = '1';
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public int numIslands(char[][] grid) {
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final int rows = grid.length, columns = grid[0].length;
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int islands = 0;
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for (int row = 0 ; row < rows ; row++) {
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for (int column = 0 ; column < columns ; column++) {
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if (isIsland(grid[row][column])) {
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islands++;
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markIslandAsSeen(grid, row, column);
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}
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}
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}
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return islands;
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}
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private boolean isIsland(char c) {
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return c == ISLAND;
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}
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private void markIslandAsSeen(char[][] grid, int row, int column) {
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if (!isValidPosition(grid, row, column) || !isIsland(grid[row][column])) return;
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markVisited(grid, row, column);
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markIslandAsSeen(grid, row - 1, column);
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markIslandAsSeen(grid, row, column + 1);
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markIslandAsSeen(grid, row + 1, column);
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markIslandAsSeen(grid, row, column - 1);
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}
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private boolean isValidPosition(char[][] grid, int row, int column) {
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return row >= 0
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&& row < grid.length
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&& column >= 0
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&& column < grid[0].length;
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}
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private boolean alreadyVisited(char c) {
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return c == VISITED;
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}
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private void markVisited(char[][] grid, int row, int column) {
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grid[row][column] = VISITED;
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}
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}

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