[LeetCode] Problem 240 - Search a 2D Matrix II

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Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

  • Integers in each row are sorted in ascending from left to right.
  • Integers in each column are sorted in ascending from top to bottom.

Example

Consider the following matrix:

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[
  [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.

Code

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public boolean searchMatrix(int[][] matrix, int target) {
    int i = matrix.length - 1;
    int j = 0;

    while (i >= 0 && j < matrix[0].length) {
        if (matrix[i][j] < target)
            j++;
        else if (matrix[i][j] > target)
            i--;
        else
            return true;
    }

    return false;
}