[LeetCode][JavaScript]Search a 2D Matrix

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/

虽然是个二维数组，但是有序，当成一维数组二分，计算出row和col的下标。

如果错用两次二分，一次做行一次做列，写起来就很复杂了。

/**
* @param {number[][]} matrix
* @param {number} target
* @return {boolean}
*/
var searchMatrix = function(matrix, target) {
var m = matrix.length, n = matrix[0].length;
var i  = 0, j = m * n - 1, middle, row, col, curr;
while(i <= j){
middle = parseInt((i + j) / 2);
row = parseInt(middle / n);
col = middle % n;
curr = matrix[row][col];
if(target === curr){
return true;
}

if(target > curr){
i = middle + 1;
}else{
j = middle - 1;
}
}
return false;
};