[LeetCode] Read N Characters Given Read4 I & II

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) {
         char tmp[];
         int idx = , cnt4;
         while (idx < n) {
             cnt4 = read4(tmp);
             for (int i = ; i < cnt4 && idx < n; ++i) {
                 buf[idx++] = tmp[i];
             }
             if (cnt4 < ) break;
         }
         return idx;
     }
 };

Read N Characters Given Read4 II - Call multiple times

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 may be called multiple times.

 // Forward declaration of the read4 API.
 int read4(char *buf);

 class Solution {
 private:
     char tmp[];
     int tmp_idx = , tmp_len = ;
 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 idx = ;
         bool flag;
         while (idx < n) {
             flag = true;
             if (tmp_idx == tmp_len) {
                 tmp_idx = ;
                 tmp_len = read4(tmp);
                 if (tmp_len != ) flag = false;
             }
             for (; tmp_idx < tmp_len && idx < n; ++tmp_idx) {
                 buf[idx++] = tmp[tmp_idx];
             }
             if (!flag) break;
         }
         return idx;
     }
 };