Algorithm
Problem Name: 393. UTF-8 Validation
Given an integer array data representing the data, return whether it is a valid UTF-8 encoding (i.e. it translates to a sequence of valid UTF-8 encoded characters).
A character in UTF8 can be from 1 to 4 bytes long, subjected to the following rules:
- For a 1-byte character, the first bit is a
0, followed by its Unicode code. - For an n-bytes character, the first
nbits are all one's, then + 1bit is0, followed byn - 1bytes with the most significant2bits being10.
This is how the UTF-8 encoding would work:
Number of Bytes | UTF-8 Octet Sequence
| (binary)
--------------------+-----------------------------------------
1 | 0xxxxxxx
2 | 110xxxxx 10xxxxxx
3 | 1110xxxx 10xxxxxx 10xxxxxx
4 | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
x denotes a bit in the binary form of a byte that may be either 0 or 1.
Note: The input is an array of integers. Only the least significant 8 bits of each integer is used to store the data. This means each integer represents only 1 byte of data.
Example 1:
Input: data = [197,130,1] Output: true Explanation: data represents the octet sequence: 11000101 10000010 00000001. It is a valid utf-8 encoding for a 2-bytes character followed by a 1-byte character.
Example 2:
Input: data = [235,140,4] Output: false Explanation: data represented the octet sequence: 11101011 10001100 00000100. The first 3 bits are all one's and the 4th bit is 0 means it is a 3-bytes character. The next byte is a continuation byte which starts with 10 and that's correct. But the second continuation byte does not start with 10, so it is invalid.
Constraints:
1 <= data.length <= 2 * 1040 <= data[i] <= 255
Code Examples
#1 Code Example with C Programming
Code -
C Programming
bool validUtf8(int* data, int dataSize) {
int i, n;
unsigned char k;
n = 0;
for (i = 0; i < dataSize; i ++) {
k = data[i] & 0xff;
if (n) {
if ((k & 0xc0) != 0x80) {
return false;
}
n --;
} else {
while (k & 0x80) {
k = k << 1;
n ++;
}
if (n) {
if (n == 1 || n > 4) return false;
n --;
}
}
}
if (n) return false;
return true;
}
Input
Output
#2 Code Example with Java Programming
Code -
Java Programming
class Solution {
public boolean validUtf8(int[] data) {
int numberOfBytes = 0;
for (int i = 0; i < data.length; i++) {
String binaryRep = Integer.toBinaryString(data[i]);
binaryRep = binaryRep.length() >= 8 ?
binaryRep.substring(binaryRep.length() - 8) :
"00000000".substring(binaryRep.length() % 8) + binaryRep;
if (numberOfBytes == 0) {
for (int j = 0; j < binaryRep.length(); j++) {
if (binaryRep.charAt(j) == '0') {
break;
}
numberOfBytes++;
}
if (numberOfBytes == 0) {
continue;
}
if (numberOfBytes > 4 || numberOfBytes == 1) {
return false;
}
} else {
if (!(binaryRep.charAt(0) == '1' && binaryRep.charAt(1) == '0')) {
return false;
}
}
numberOfBytes--;
}
return numberOfBytes == 0;
}
}
Input
Output
#3 Code Example with Javascript Programming
Code -
Javascript Programming
const validUtf8 = function(data) {
let count = 0
for (let c of data) {
if (count === 0) {
if (c >> 5 === 0b110) count = 1
else if (c >> 4 === 0b1110) count = 2
else if (c >> 3 === 0b11110) count = 3
else if (c >> 7) return false
} else {
if (c >> 6 !== 0b10) return false
count--
}
}
return count == 0
}
Input
Output
#4 Code Example with Python Programming
Code -
Python Programming
class Solution:
def validUtf8(self, data: List[int]) -> bool:
def rest(i):
if len(data) < i:
return False
for _ in range(i):
if not data.pop().startswith("10"):
return False
return True
data, byte = [str(bin(seq)[2:].zfill(8)) for seq in data[::-1]], None
while data:
seq = data.pop()
if seq.startswith("0"):
continue
elif seq.startswith("110"):
if not rest(1):
return False
elif seq.startswith("1110"):
if not rest(2):
return False
elif seq.startswith("11110"):
if not rest(3):
return False
else:
return False
return True
Input
Output
#5 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _0393_UTF8Validation
{
public bool ValidUtf8(int[] data)
{
int numberOfBytesToProcess = 0;
int mask1 = 1 << 7;
int mask2 = 1 << 6;
foreach (int num in data)
{
if (numberOfBytesToProcess == 0)
{
int mask = mask1;
while ((mask & num) != 0)
{
numberOfBytesToProcess++;
mask >>= 1;
}
if (numberOfBytesToProcess == 0) continue;
if (numberOfBytesToProcess > 4 || numberOfBytesToProcess == 1) return false;
}
else
{
if ((num & mask1) == 0 || (mask2 & num) == 1)
return false;
}
numberOfBytesToProcess -= 1;
}
return numberOfBytesToProcess == 0;
}
}
}
Input
Output