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| 1 | +/** |
| 2 | + * ๊ทธ๋ํ ์ญ๋ฐฉํฅ ํ์ : DFS๋ฅผ ์ฌ์ฉํ์ฌ ํํ์๊ณผ ๋์์์ ๋๋ฌํ ์ ์๋ ๋ชจ๋ ์ง์ ์ ์ฐพ๋ ๋ฌธ์ |
| 3 | + * ์๊ฐ ๋ณต์ก๋: O(m ร n) - ๊ฐ ์
์ ์ต๋ 2๋ฒ ๋ฐฉ๋ฌธ |
| 4 | + * ๊ณต๊ฐ ๋ณต์ก๋: O(m ร n) - visited ๋ฐฐ์ด๊ณผ ์คํ ๊ณต๊ฐ |
| 5 | + */ |
| 6 | +/** |
| 7 | + * @param {number[][]} heights |
| 8 | + * @return {number[][]} |
| 9 | + */ |
| 10 | +var pacificAtlantic = function (heights) { |
| 11 | + if (!heights || heights.length === 0) return []; |
| 12 | + |
| 13 | + const m = heights.length; |
| 14 | + const n = heights[0].length; |
| 15 | + |
| 16 | + // ๋นํธ๋ง์คํน ์ฌ์ฉํ ๋ฐฉ๋ฌธ ์ํ ๊ด๋ฆฌ |
| 17 | + // 0: ๋ฏธ๋ฐฉ๋ฌธ, 1: ํํ์๋ง, 2: ๋์์๋ง, 3: ๋ ๋ค |
| 18 | + const visited = Array(m) |
| 19 | + .fill() |
| 20 | + .map(() => Array(n).fill(0)); |
| 21 | + const directions = [ |
| 22 | + [-1, 0], |
| 23 | + [1, 0], |
| 24 | + [0, -1], |
| 25 | + [0, 1], |
| 26 | + ]; |
| 27 | + const result = []; |
| 28 | + |
| 29 | + // DFS - ์คํ ์ฌ์ฉ |
| 30 | + function dfs(startPoints, oceanMask) { |
| 31 | + const stack = [...startPoints]; |
| 32 | + |
| 33 | + while (stack.length > 0) { |
| 34 | + const [row, col] = stack.pop(); |
| 35 | + |
| 36 | + // ์ด๋ฏธ ํด๋น ๋ฐ๋ค๋ก ํ์๋์ด ์์ผ๋ฉด ๊ฑด๋๋ฐ๊ธฐ |
| 37 | + if (visited[row][col] & oceanMask) continue; |
| 38 | + |
| 39 | + // ํ์ฌ ๋ฐ๋ค ํ์ |
| 40 | + visited[row][col] |= oceanMask; |
| 41 | + |
| 42 | + // ์์ชฝ ๋ฐ๋ค ๋ชจ๋ ๋๋ฌ ๊ฐ๋ฅํ๋ฉด ๊ฒฐ๊ณผ์ ์ถ๊ฐ |
| 43 | + if (visited[row][col] === 3) { |
| 44 | + result.push([row, col]); |
| 45 | + } |
| 46 | + |
| 47 | + // 4๋ฐฉํฅ ํ์ |
| 48 | + for (const [dr, dc] of directions) { |
| 49 | + const newRow = row + dr; |
| 50 | + const newCol = col + dc; |
| 51 | + |
| 52 | + // ๊ฒฝ๊ณ ํ์ธ ๋ฐ ๋์ด ์กฐ๊ฑด ํ์ธ |
| 53 | + if ( |
| 54 | + newRow >= 0 && |
| 55 | + newRow < m && |
| 56 | + newCol >= 0 && |
| 57 | + newCol < n && |
| 58 | + heights[newRow][newCol] >= heights[row][col] && |
| 59 | + !(visited[newRow][newCol] & oceanMask) |
| 60 | + ) { |
| 61 | + stack.push([newRow, newCol]); |
| 62 | + } |
| 63 | + } |
| 64 | + } |
| 65 | + } |
| 66 | + |
| 67 | + // ํํ์ ์์์ ๋ค |
| 68 | + const pacificStarts = []; |
| 69 | + for (let i = 0; i < m; i++) pacificStarts.push([i, 0]); // ์ฒซ ๋ฒ์งธ ์ด |
| 70 | + for (let j = 1; j < n; j++) pacificStarts.push([0, j]); // ์ฒซ ๋ฒ์งธ ํ (์ค๋ณต ์ ๊ฑฐ) |
| 71 | + |
| 72 | + // ๋์์ ์์์ ๋ค |
| 73 | + const atlanticStarts = []; |
| 74 | + for (let i = 0; i < m; i++) atlanticStarts.push([i, n - 1]); // ๋ง์ง๋ง ์ด |
| 75 | + for (let j = 0; j < n - 1; j++) atlanticStarts.push([m - 1, j]); // ๋ง์ง๋ง ํ (์ค๋ณต ์ ๊ฑฐ) |
| 76 | + |
| 77 | + // ๊ฐ ๋ฐ๋ค์์ DFS ์คํ |
| 78 | + dfs(pacificStarts, 1); // ํํ์: ๋นํธ 1 |
| 79 | + dfs(atlanticStarts, 2); // ๋์์: ๋นํธ 2 |
| 80 | + |
| 81 | + return result; |
| 82 | +}; |
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