解题思路

见代码，很简单，不解释

157. 用 Read4 读取 N 个字符

代码

"""
The read4 API is already defined for you.

    @param buf4, a list of characters
    @return an integer
    def read4(buf4):

# Below is an example of how the read4 API can be called.
file = File("abcdefghijk") # File is "abcdefghijk", initially file pointer (fp) points to 'a'
buf4 = [' '] * 4 # Create buffer with enough space to store characters
read4(buf4) # read4 returns 4. Now buf = ['a','b','c','d'], fp points to 'e'
read4(buf4) # read4 returns 4. Now buf = ['e','f','g','h'], fp points to 'i'
read4(buf4) # read4 returns 3. Now buf = ['i','j','k',...], fp points to end of file
"""

class Solution:
    def read(self, buf, n):
        """
        :type buf: Destination buffer (List[str])
        :type n: Number of characters to read (int)
        :rtype: The number of actual characters read (int)
        """
        index = 0
        buf4 = [' '] * 4
        while index < n:
            m = read4(buf4)
            for i in range(m):
                buf[index] = buf4[i]
                index += 1
                if index >= n: break
            if m != 4: break
        return index

效果图