LeetCode Q157: Read N Characters Given Read4

The API: int read4(char *buf) reads 4 characters at a time from a file.

The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the file.

By using the read4 API, implement the function int read(char *buf, int n) that reads n characters from the file.

Note:
The read function will only be called once for each test case.

	// Forward declaration of the read4 API.
	int read4(char *buf);
	class Solution {
	public:
	/**
	* @param buf Destination buffer
	* @param n Maximum number of characters to read
	* @return The number of characters read
	*/
	int read(char *buf, int n) {
	int p=0;
	int count=0;
	while(true){
	char _buf[4];
	int _n=read4(_buf);
	for(int i=0; i<_n; i++){
	if(count==n)
	return n;
	buf[p++]=_buf[i];
	count++;
	}
	if(_n<4)
	return count;
	}
	}
	};

view raw Q157ReadCharGivenRead4.cpp hosted with ❤ by GitHub

Round 2 solution:

	// Forward declaration of the read4 API.
	int read4(char *buf);
	class Solution {
	public:
	/**
	* @param buf Destination buffer
	* @param n Maximum number of characters to read
	* @return The number of characters read
	*/
	int read(char *buf, int n) {
	int res=0;
	int local=4;
	while(res<n&&local==4){
	local=read4(buf);
	res+=local;
	buf+=local;
	}
	return min(n, res);
	}
	};

view raw Q157Rnd2.cpp hosted with ❤ by GitHub