Create 393. UTF-8 Validation.java

Author: futurus

393. UTF-8 Validation.java

@@ -0,0 +1,48 @@
+public class Solution {
+    public boolean validUtf8(int[] data) {
+        ArrayList<String> octs = new ArrayList<>();
+        
+        for (int i : data) {
+            octs.add(Integer.toBinaryString( (1 << 8) | i ).substring( 1 ));
+        }
+        
+        int cIndex = 0;
+        
+        while (cIndex < data.length) {
+            String b = octs.get(cIndex);
+            
+            if (b.substring(0, 5).equals("11110")) { // check 4-byte
+                if (cIndex + 3 >= octs.size() 
+                    || !octs.get(cIndex+1).substring(0, 2).equals("10")
+                    || !octs.get(cIndex+2).substring(0, 2).equals("10")
+                    || !octs.get(cIndex+3).substring(0, 2).equals("10")) {
+                    return false;
+                }
+                
+                cIndex += 4;
+            } else if (b.substring(0, 4).equals("1110")) { // check 3-byte
+                
+                if (cIndex + 2 >= octs.size() 
+                    || !octs.get(cIndex+1).substring(0, 2).equals("10")
+                    || !octs.get(cIndex+2).substring(0, 2).equals("10")) {
+                    return false;
+                }
+                
+                cIndex += 3;
+            } else if (b.substring(0, 3).equals("110")) {  // check 2-byte
+                if (cIndex + 1 >= octs.size() 
+                    || !octs.get(cIndex+1).substring(0, 2).equals("10")) {
+                    return false;
+                }
+                
+                cIndex += 2;
+            } else if (b.substring(0, 1).equals("0")) { // check 1-byte
+                cIndex += 1;
+            } else {
+                return false;
+            }
+        }
+        
+        return true;
+    }
+}