[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;
};