Baidu PHP Internship one side of the test-algorithm-two-dimensional ordered matrix lookup

Title Description

There is a two-dimensional matrix, each row of elements, left to right to maintain a strict increment, the elements of each column, from top to bottom to maintain a strict increment. Finds the given element Elem, returning null or element position.

1	3	7	15	16
2	5	8	17	19
3	6	9	18	20
7	18	20	22	24
9	23	24	28	33

Thinking first from the diagonal, the upper left is the minimum matrix, the lower right corner is the maximum value, not within the interval, the value of the lookup is not within the matrix, otherwise: from the lower left corner, if the current element is greater than elem, then go up; Complexity O (m+n).

Baidu PHP Internship one side of the test-algorithm-two-dimensional ordered matrix lookup