Question

10.09. Sorted Matrix Search

中文文档

Description

Given an M x N matrix in which each row and each column is sorted in ascending order, write a method to find an element.

Example:

Given matrix:

[

  [1,   4,  7, 11, 15],

  [2,   5,  8, 12, 19],

  [3,   6,  9, 16, 22],

  [10, 13, 14, 17, 24],

  [18, 21, 23, 26, 30]

]

Given target = 5, return true.

Given target = 20, return false.

Solutions

Solution 1

class Solution:
  def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
    if not matrix or not matrix[0]:
      return False
    m, n = len(matrix), len(matrix[0])
    i, j = m - 1, 0
    while i >= 0 and j < n:
      if matrix[i][j] == target:
        return True
      if matrix[i][j] > target:
        i -= 1
      else:
        j += 1
    return False

class Solution {
  public boolean searchMatrix(int[][] matrix, int target) {
    if (matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0) {
      return false;
    }
    int m = matrix.length, n = matrix[0].length;
    int i = m - 1, j = 0;
    while (i >= 0 && j < n) {
      if (matrix[i][j] == target) {
        return true;
      }
      if (matrix[i][j] > target) {
        --i;
      } else {
        ++j;
      }
    }
    return false;
  }
}

class Solution {
public:
  bool searchMatrix(vector<vector<int>>& matrix, int target) {
    if (matrix.size() == 0 || matrix[0].size() == 0) return false;
    int m = matrix.size(), n = matrix[0].size();
    int i = m - 1, j = 0;
    while (i >= 0 && j < n) {
      if (matrix[i][j] == target) return true;
      if (matrix[i][j] > target)
        --i;
      else
        ++j;
    }
    return false;
  }
};

func searchMatrix(matrix [][]int, target int) bool {
  if len(matrix) == 0 || len(matrix[0]) == 0 {
    return false
  }
  m, n := len(matrix), len(matrix[0])
  i, j := m-1, 0
  for i >= 0 && j < n {
    if matrix[i][j] == target {
      return true
    }
    if matrix[i][j] > target {
      i--
    } else {
      j++
    }
  }
  return false
}