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leetcode-200-NumberOfIslands.js
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leetcode-200-NumberOfIslands.js
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// /**
// * @param {character[][]} grid
// * @return {number}
// */
// p: array: m x n 2d binary: string 1 land & 0 water
// r: num => f(n) numbers of islands (numbers of groups of '1')
// e:
// base cases:
// [['0']] => 0
// [['1']] => 1
// 1 1
// 1 1
// 1 1
// f(0,0) => 0
// f(1,1) => 0 1
// f(y,x) = f(y+1,x) && f(y,x+1)
// Input: grid = [
// ["1","1","1","1","0"],
// ["1","1","0","1","0"],
// ["1","1","0","0","0"],
// ["0","0","0","0","0"]
// ]
// Output: 1
// Input: grid = [
// ["1","1","0","0","0"],
// ["1","1","0","0","0"],
// ["0","0","1","0","0"],
// ["0","0","0","1","1"]
// ]
// Output: 3
var numIslands = function (grid) {
//
const setOfGrid = new Set();
// for (let i = 1; i < grid.length; i++) {
let count = 0;
let stack = [];
for (let i = 0; i < grid.length; i++) {
for (let j = 0; j < grid[0].length; j++) {
if (grid[i][j] === "1" && !setOfGrid.has(`${i},${j}`)) {
stack.push([i, j]);
count++;
}
// console.log(i, j, setOfGrid.has(`${i},${j}`));
while (stack.length > 0) {
console.log(
stack
// setOfGrid
// // i, j, setOfGrid.has(`${i},${j}`)
);
const [y, x] = stack.pop();
if (!setOfGrid.has(`${y},${x}`)) {
setOfGrid.add(`${y},${x}`);
y + 1 < grid.length &&
grid[y + 1][x] === "1" &&
stack.push([y + 1, x]);
x + 1 < grid[0].length &&
grid[y][x + 1] === "1" &&
stack.push([y, x + 1]);
y - 1 >= 0 && grid[y - 1][x] === "1" && stack.push([y - 1, x]);
x - 1 >= 0 && grid[y][x - 1] === "1" && stack.push([y, x - 1]);
}
}
}
}
console.log(count);
return count;
};
// numIslands([
// ["1", "1", "0", "0", "0"],
// ["1", "1", "0", "0", "0"],
// ["0", "0", "1", "0", "0"],
// ["0", "0", "0", "1", "1"],
// ]);
// numIslands([
// ["1", "1", "1", "1", "0"],
// ["1", "1", "0", "1", "0"],
// ["1", "1", "0", "0", "0"],
// ["0", "0", "0", "0", "0"],
// ]);
numIslands([
["1", "1", "1"],
["0", "1", "0"],
["1", "1", "1"],
]);