LeetCode 74. Search a 2D Matrix (Search 2D Matrix) solution ideas and methods

LeetCode 74. Search a 2D Matrix (Search 2D Matrix) solution ideas and methods

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 from left to right.
• The first integer of each row is greater than the last integer of the previous row.

   

  For example,

  Consider the following matrix:

  [  [1,   3,  5,  7],  [10, 11, 16, 20],  [23, 30, 34, 50]]

  Given target =3, Returntrue.

  Idea: This question is relatively simple. It is mainly used for the first column and then for the specific row by using two bipartite methods.

  The Code is as follows:

   

  Public class Solution {public boolean searchMatrix (int [] [] m, int target) {// two binary searches // first searches for the first column and finds the row, then search for the int I = 0; int j = m. length-1; int mid = 0; // search for the first column while (I <= j) {mid = (I + j)/2; if (m [mid] [0] = target) {return true;} else if (m [mid] [0] <target) {I = mid + 1 ;} else {j = mid-1 ;}}if (m [mid] [0]> target) {if (mid = 0) {return false ;} mid --; // mid-1} // search for mid rows I = 0; j = m [0]. length-1; int k = mid; // returns true while (I <= j) {mid = (I + j)/2; if (m [k] [mid] = target) {return true;} else if (m [k] [mid] <target) {I = mid + 1 ;} else {j = mid-1 ;}/// If no result is found, false return false;} is returned ;}}