28. 搜索二维矩阵

写出一个高效的算法来搜索 m × n矩阵中的值。

这个矩阵具有以下特性：

每行中的整数从左到右是排序的。
每行的第一个数大于上一行的最后一个整数。

样例
考虑下列矩阵：

[
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
给出 target = 3，返回 true

Python:

class Solution:
"""
@param matrix, a list of lists of integers
@param target, an integer
@return a boolean, indicate whether matrix contains target
"""
def searchMatrix(self, matrix, target):
    for i in range(len(matrix) - 1):
        if target >= matrix[i][0] and target < matrix[i + 1][0]:
            for j in range(len(matrix[i])):
                if target == matrix[i][j]:
                    return True
        else:
            for j in range(len(matrix[i + 1])):
                if target == matrix[i + 1][j]:
                    return True
    return False


 # method 2
class Solution:
"""
@param matrix, a list of lists of integers
@param target, an integer
@return a boolean, indicate whether matrix contains target
"""
def searchMatrix(self, matrix, target):
    if len(matrix) == 0:
        return False
    n, m = len(matrix), len(matrix[0])
    left, right = 0, n * m - 1
    while left + 1 < right:
        mid = (left + right) / 2
        i, j = mid / m, mid % m
        if target == matrix[i][j]:
            return True
        elif target < matrix[i][j]:
            right = mid - 1
        else:
            left = mid + 1
    i, j = left / m, left % m
    if target == matrix[i][j]:
        return True
    i, j = right / m, right % m
    if target == matrix[i][j]:
        return True
    return False