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Leetcode240-searchA2DMatrixII

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Solution Report of LeetCode Acceptted

Description

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

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Consider the following 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.

Solution

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