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1765. Map of Highest Peak 👍

  • Time: $O(mn)$
  • Space: $O(mn)$
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class Solution {
 public:
  vector<vector<int>> highestPeak(vector<vector<int>>& isWater) {
    const int m = isWater.size();
    const int n = isWater[0].size();
    const vector<int> dirs{0, 1, 0, -1, 0};
    vector<vector<int>> ans(m, vector<int>(n, -1));
    queue<pair<int, int>> q;

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        if (isWater[i][j] == 1) {
          q.emplace(i, j);
          ans[i][j] = 0;
        }

    while (!q.empty()) {
      const auto [i, j] = q.front();
      q.pop();
      for (int k = 0; k < 4; ++k) {
        const int x = i + dirs[k];
        const int y = j + dirs[k + 1];
        if (x < 0 || x == m || y < 0 || y == n)
          continue;
        if (ans[x][y] != -1)
          continue;
        ans[x][y] = ans[i][j] + 1;
        q.emplace(x, y);
      }
    }

    return ans;
  }
};

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class Solution {
  public int[][] highestPeak(int[][] isWater) {
    final int m = isWater.length;
    final int n = isWater[0].length;
    final int[] dirs = {0, 1, 0, -1, 0};
    int[][] ans = new int[m][n];
    Arrays.stream(ans).forEach(A -> Arrays.fill(A, -1));
    Queue<Pair<Integer, Integer>> q = new ArrayDeque<>();

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        if (isWater[i][j] == 1) {
          q.offer(new Pair<>(i, j));
          ans[i][j] = 0;
        }

    while (!q.isEmpty()) {
      final int i = q.peek().getKey();
      final int j = q.poll().getValue();
      for (int k = 0; k < 4; ++k) {
        final int x = i + dirs[k];
        final int y = j + dirs[k + 1];
        if (x < 0 || x == m || y < 0 || y == n)
          continue;
        if (ans[x][y] != -1)
          continue;
        ans[x][y] = ans[i][j] + 1;
        q.offer(new Pair<>(x, y));
      }
    }

    return ans;
  }
}

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class Solution:
  def highestPeak(self, isWater: List[List[int]]) -> List[List[int]]:
    m = len(isWater)
    n = len(isWater[0])
    dirs = [0, 1, 0, -1, 0]
    ans = [[-1] * n for _ in range(m)]
    q = collections.deque()

    for i in range(m):
      for j in range(n):
        if isWater[i][j] == 1:
          q.append((i, j))
          ans[i][j] = 0

    while q:
      i, j = q.popleft()
      for k in range(4):
        x = i + dirs[k]
        y = j + dirs[k + 1]
        if x < 0 or x == m or y < 0 or y == n:
          continue
        if ans[x][y] != -1:
          continue
        ans[x][y] = ans[i][j] + 1
        q.append((x, y))

    return ans