Home
Algorithms Data Structures Interview Experiences
Amazon Google Facebook Microsoft Apple Netflix
Play 2048 How to

LeetCode Solutions

158. Read N Characters Given read4 II - Call Multiple Times

Time: $O(n)$

Space: $O(1)$

			


/**
 * The read4 API is defined in the parent class Reader4.
 *     int read4(char *buf4);
 */

class Solution {
 public:
  /**
   * @param buf Destination buffer
   * @param n   Number of characters to read
   * @return    The number of actual characters read
   */
  int read(char* buf, int n) {
    int i = 0;  // buf's index

    while (i < n) {
      if (i4 == n4) {      // All characters in buf4 are consumed
        i4 = 0;            // Reset buf4's index
        n4 = read4(buf4);  // Read 4 (or less) chars from file to buf4
        if (n4 == 0)       // Reach the EOF
          return i;
      }
      buf[i++] = buf4[i4++];
    }

    return i;
  }

 private:
  char* buf4 = new char[4];
  int i4 = 0;  // buf4's index
  int n4 = 0;  // buf4's size
};




			


/**
 * The read4 API is defined in the parent class Reader4.
 *     int read4(char[] buf4);
 */

public class Solution extends Reader4 {
  /**
   * @param buf Destination buffer
   * @param n   Number of characters to read
   * @return    The number of actual characters read
   */
  public int read(char[] buf, int n) {
    int i = 0; // buf's index

    while (i < n) {
      if (i4 == n4) {     // All characters in buf4 are consumed
        i4 = 0;           // Reset buf4's index
        n4 = read4(buf4); // Read 4 (or less) chars from file to buf4
        if (n4 == 0)      // Reach the EOF
          return i;
      }
      buf[i++] = buf4[i4++];
    }

    return i;
  }

  private char[] buf4 = new char[4];
  private int i4 = 0; // buf4's index
  private int n4 = 0; // buf4's size
}




			


# The read4 API is already defined for you.
# Def read4(buf4: List[str]) -> int:

class Solution:
  def read(self, buf: List[str], n: int) -> int:
    i = 0  # buf's index

    while i < n:
      if self.i4 == self.n4:  # All characters in buf4 are consumed
        self.i4 = 0  # Reset buf4's index
        self.n4 = read4(self.buf4)  # Read 4 (or less) chars from file to buf4
        if self.n4 == 0:  # Reach the EOF
          return i
      buf[i] = self.buf4[self.i4]
      i += 1
      self.i4 += 1

    return i

  buf4 = [' '] * 4
  i4 = 0  # buf4's index
  n4 = 0  # buf4's size