[LeetCode][JavaScript]Search a 2D Matrix

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Search a 2D Matrix

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, return true.

https://leetcode.com/problems/search-a-2d-matrix/

 

 

 

 

 

 

雖然是個二維數組，但是有序，當成一維數組二分，計算出row和col的下標。

如果錯用兩次二分，一次做行一次做列，寫起來就很複雜了。

 1 /** 2  * @param {number[][]} matrix 3  * @param {number} target 4  * @return {boolean} 5  */ 6 var searchMatrix = function(matrix, target) { 7     var m = matrix.length, n = matrix[0].length; 8     var i  = 0, j = m * n - 1, middle, row, col, curr; 9     while(i <= j){10         middle = parseInt((i + j) / 2);11         row = parseInt(middle / n);12         col = middle % n;13         curr = matrix[row][col];14         if(target === curr){15             return true;16         }17 18         if(target > curr){19             i = middle + 1; 20         }else{21             j = middle - 1;22         }    23     }24     return false;25 };

 

 

[LeetCode][JavaScript]Search a 2D Matrix