leetcode JAVA Search a 2D Matrix 难度系数3 3.25

Question：

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

.

public class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
int row = matrix.length;
int col = matrix[0].length;
int[] temp = new int[row * col];
int count = 0;
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
temp[count++] = matrix[i][j];
}
}
int low = 0;
int high = row * col-1;
int mid = -1;
while (low <= high) {
mid = (low + high) / 2;
if (temp[mid] == target) {
return true;
} else if (temp[mid] > target) {
high = mid - 1;
} else {
low = mid + 1;
}
}
return false;
}
}

public class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
int row = matrix.length;
int col = matrix[0].length;
int low = 0;
int high = row * col - 1;
int mid = -1;
while (low <= high) {
mid = (low + high) / 2;
if (matrix[mid/col][mid%col] == target) {
return true;
} else if (matrix[mid/col][mid%col] > target) {
high = mid - 1;
} else {
low = mid + 1;
}
}
return false;
}
}