2015年8月31日星期一

Search a 2D Matrix II

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.
For example,
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.

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

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