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1428. Leftmost Column with at Least a One 👍

  • Time: $O(m\log n)$
  • Space: $O(1)$
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/**
 * // This is the BinaryMatrix's API interface.
 * // You should not implement it, or speculate about its implementation
 * class BinaryMatrix {
 *  public:
 *   int get(int row, int col);
 *   vector<int> dimensions();
 * };
 */

class Solution {
 public:
  int leftMostColumnWithOne(BinaryMatrix& binaryMatrix) {
    const vector<int> dimensions = binaryMatrix.dimensions();
    const int m = dimensions[0];
    const int n = dimensions[1];
    int ans = -1;
    int l = 0;
    int r = n - 1;

    while (l <= r) {
      const int mid = (l + r) / 2;
      if (existOne(binaryMatrix, m, mid)) {
        ans = mid;
        r = mid - 1;
      } else {
        l = mid + 1;
      }
    }

    return ans;
  }

 private:
  bool existOne(BinaryMatrix& binaryMatrix, int m, int col) {
    for (int i = 0; i < m; ++i)
      if (binaryMatrix.get(i, col) == 1)
        return true;
    return false;
  }
};

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/**
 * // This is the BinaryMatrix's API interface.
 * // You should not implement it, or speculate about its implementation
 * interface BinaryMatrix {
 *   public int get(int row, int col) {}
 *   public List<Integer> dimensions {}
 * };
 */

class Solution {
  public int leftMostColumnWithOne(BinaryMatrix binaryMatrix) {
    final List<Integer> dimensions = binaryMatrix.dimensions();
    final int m = dimensions.get(0);
    final int n = dimensions.get(1);
    int ans = -1;
    int l = 0;
    int r = n - 1;

    while (l <= r) {
      final int mid = (l + r) / 2;
      if (existOne(binaryMatrix, m, mid)) {
        ans = mid;
        r = mid - 1;
      } else {
        l = mid + 1;
      }
    }

    return ans;
  }

  private boolean existOne(BinaryMatrix binaryMatrix, int m, int col) {
    for (int i = 0; i < m; ++i)
      if (binaryMatrix.get(i, col) == 1)
        return true;
    return false;
  }
}

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# """
# This is BinaryMatrix's API interface.
# You should not implement it, or speculate about its implementation
# """
# Class BinaryMatrix(object):
#   def get(self, row: int, col: int) -> int:
#   def dimensions(self) -> List[int]:

class Solution:
  def leftMostColumnWithOne(self, binaryMatrix: 'BinaryMatrix') -> int:
    m, n = binaryMatrix.dimensions()
    ans = -1
    l = 0
    r = n - 1

    while l <= r:
      mid = (l + r) // 2
      if any(binaryMatrix.get(i, mid) for i in range(m)):
        ans = mid
        r = mid - 1
      else:
        l = mid + 1

    return ans
  • Time: $O(m + n)$
  • Space: $O(1)$
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/**
 * // This is the BinaryMatrix's API interface.
 * // You should not implement it, or speculate about its implementation
 * class BinaryMatrix {
 *  public:
 *   int get(int row, int col);
 *   vector<int> dimensions();
 * };
 */

class Solution {
 public:
  int leftMostColumnWithOne(BinaryMatrix& binaryMatrix) {
    const vector<int> dimensions = binaryMatrix.dimensions();
    const int m = dimensions[0];
    const int n = dimensions[1];
    int ans = -1;
    int i = 0;
    int j = n - 1;

    while (i < m && j >= 0)
      if (binaryMatrix.get(i, j) == 1)
        ans = j--;
      else
        ++i;

    return ans;
  }
};

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/**
 * // This is the BinaryMatrix's API interface.
 * // You should not implement it, or speculate about its implementation
 * interface BinaryMatrix {
 *   public int get(int row, int col) {}
 *   public List<Integer> dimensions {}
 * };
 */

class Solution {
  public int leftMostColumnWithOne(BinaryMatrix binaryMatrix) {
    final List<Integer> dimensions = binaryMatrix.dimensions();
    final int m = dimensions.get(0);
    final int n = dimensions.get(1);
    int ans = -1;
    int i = 0;
    int j = n - 1;

    while (i < m && j >= 0)
      if (binaryMatrix.get(i, j) == 1)
        ans = j--;
      else
        ++i;

    return ans;
  }
}

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# """
# This is BinaryMatrix's API interface.
# You should not implement it, or speculate about its implementation
# """
# Class BinaryMatrix(object):
#   def get(self, row: int, col: int) -> int:
#   def dimensions(self) -> List[int]:

class Solution:
  def leftMostColumnWithOne(self, binaryMatrix: 'BinaryMatrix') -> int:
    m, n = binaryMatrix.dimensions()
    ans = -1
    i = 0
    j = n - 1

    while i < m and j >= 0:
      if binaryMatrix.get(i, j):
        ans = j
        j -= 1
      else:
        i += 1

    return ans