wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
let count: number | null = null; count.toFixed(67); | let count: number | null = null; if(count!==null) count.toFixed(67); | Null check. | TypeScript |
int[] values = new int[56];
values[56] = 5; | int[] values = new int[56];
if (56 < values.length) values[56] = 5; | Check bounds. | Java |
$x = 5; if ($x -eq 5) { Write-Host 'yes' } | $x = 5; if ($x -eq 5) { Write-Host 'yes' } | Correct. | PowerShell |
a == '2' | a === 2 | Use strict equality. | JavaScript |
String name = 'message'; | String name = 'message'; | Correct. | Dart |
class Child Super: | class Child(Super): | Inheritance uses parentheses. | Python |
function compute() {{
return
{{key:'result'}}
}} | function compute() {{
return {{key:'result'}};
}} | Return object on same line. | JavaScript |
WHERE email = '46' | WHERE email = 46 | Don't quote integer. | SQL |
.User {{ color: blue; }} | .User {{ color: blue; }} | Correct. | CSS |
int* p = nullptr; *p=5; | int* p = new int; *p=5; | Allocate memory. | C++ |
list[69] | if (list.indices.contains(69)) list[69] | Check index. | Kotlin |
int val = 'value'; | String val = 'value'; | Type mismatch. | Dart |
{{"id":"test",}} | {{"id":"test"}} | Remove trailing comma. | JSON |
void main() {{ print('message') }} | void main() {{ print('message'); }} | Add semicolon. | Dart |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
List(7,59,40) | List(7,59,40) | Correct. | Scala |
cin >> x; | int x;
cin >> x; | Declare variable. | C++ |
class Person {{ int data; }}
obj.data=5; | class Person {{ public int data; }}
obj.data=5; | Make field public. | Java |
<div color=#333> | <div style='color:#333;'> | Use style attribute. | CSS |
function bar(): void {{ return 47; }} | function bar(): number {{ return 47; }} | Return type mismatch. | TypeScript |
if data = 4 {{}} | if data == 4 {{}} | Use ==. | Swift |
while item > 44
item -= 1 | while item > 44:
item -= 1 | Colon missing after while. | Python |
math.sqrt(27) | import math
math.sqrt(27) | Import module first. | Python |
if num = 96 | if num == 96 | Use ==. | MATLAB |
const index = 1; index = 100; | let index = 1; index = 100; | Cannot reassign const. | JavaScript |
let num: Int = 'result' | let num: String = 'result' | Fix type. | Swift |
let y = 'value' | let y = "value" | Double quotes. | Swift |
def handle
puts 'message'
end | def handle
puts 'message'
end | Correct. | Ruby |
else
print('test') | else:
print('test') | Colon after else. | Python |
'info' + 90 | 'info' + 90.to_s | Convert int. | Ruby |
println('world') | println("world") | Double quotes. | Scala |
val c = 92; c = 85 | var c = 92; c = 85 | Use var for reassignment. | Scala |
DELETE FROM items WHERE status=78 | DELETE FROM items WHERE status=78; | Add semicolon. | SQL |
const int x; x = 5; | const int x = 5; | Const must be initialized. | C++ |
var x = 48; | var x = 48; | Correct. | Dart |
<user><desc>message</desc><desc>87</desc></user | <user><desc>message</desc><desc>87</desc></user> | Add closing >. | XML |
if (z = 61) {{}} | if (z == 61) {{}} | Use ==. | Kotlin |
if data = 86 | if data == 86 | Use ==. | Go |
val z: Int = 'data' | val z: String = 'data' | Fix type. | Kotlin |
arr(52) | if length(arr) >= 52, arr(52), end | Check length. | MATLAB |
yield index | yield index | Correct yield. | Python |
{ "name": "message" } | { "name": "message" } | Correct. | JSON |
if (count = 6) | if (count == 6) | Use ==. | Scala |
if (index = 16) {} | if (index == 16) {} | Use ==. | Dart |
try {{ throw 'message'; }} catch(e) {{}} | try {{ throw new Error('message'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
fn compute() -> i32 {{ 9 }} | fn compute() -> i32 {{ 9 }} | Correct. | Rust |
{{'age':54, 'status' 31}} | {{'age':54, 'status':31}} | Colon missing. | Python |
63temp = 10 | temp63 = 10 | Variable cannot start with digit. | Python |
with open('input.csv') as fp:
data = fp.read() | with open('input.csv') as fp:
data = fp.read() | Correct. | Python |
<p>hello <b>world</p></b> | <p>hello <b>world</b></p> | Nest properly. | HTML |
let data = 51; | let data = 51; | Correct. | JavaScript |
if z = 46 | if z == 46 | Use ==. | Ruby |
String bar = 'test'; | String bar = "test"; | Double quotes. | Java |
for i=1,60 do print(i) end | for i=1,60 do print(i) end | Correct. | Lua |
raise 'hello' | raise Exception('hello') | Raise needs an exception class. | Python |
$data[49] | if ($data.Count -gt 49) {{ $data[49] }} | Check bounds. | PowerShell |
int data[22]; data[22]=5; | int data[22]; if(22<22){{}} else data[22]=5; | Bounds check. | C++ |
let a = 55; let a = 96; | let a = 55; a = 96; | Duplicate declaration. | JavaScript |
let a = 47; a += 1; | let mut a = 47; a += 1; | Need mut to modify. | Rust |
if (data) console.log('yes') else console.log('no') | if (data) console.log('yes'); else console.log('no'); | Missing semicolon. | JavaScript |
{{"name":"result" "title":97}} | {{"name":"result", "title":97}} | Add comma. | JSON |
const foo; | const foo = 49; | Initialize const. | JavaScript |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(80); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(80, () => console.log('listening')); | Add callback. | Node.js |
[x*x for x in items if x > 1] | [x*x for x in items if x > 1] | Correct list comprehension. | Python |
for item in range(78)
print(item) | for item in range(78):
print(item) | Colon after for. | Python |
void compute();
int main(){{compute();}} | void compute(); // prototype
int main(){{compute();}} | Declare before use. | C++ |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
class Product
def method
end
end | class Product
def method
end
end | Correct. | Ruby |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
let vec=vec![47,77,73]; let first=&vec[0]; vec.push(90); | let mut vec=vec![47,77,73]; let first=vec[0]; vec.push(90); | Copy instead of reference. | Rust |
System.out.println('data') | System.out.println('data'); | Add semicolon. | Java |
baz | baz() | Add parentheses. | Kotlin |
if z > 53
print('test') | if z > 53:
print('test') | Colon missing after if. | Python |
'result' + 35 | 'result' + str(35) | Can't add int to string. | Python |
echo 'hello' | echo 'hello'; | Add semicolon. | PHP |
class = 'info' | class_name = 'info' | 'class' is a keyword. | Python |
def test(index):
return index + 1 | def test(index):
return index + 1 | Correct. | Python |
if ($bar = 96) {{}} | if ($bar -eq 96) {{}} | Use -eq. | PowerShell |
if (a = 35) {{}} | if (a == 35) {{}} | Use ==. | Java |
<root><child>text</child></root> | <root><child>text</child></root> | Correct. | XML |
[83, 81, 71 | [83, 81, 71] | Close bracket. | Ruby |
if (foo = 34) | if (foo == 34) | Use ==. | R |
<person age=95> | <person age="95"> | Quote attribute. | XML |
<input type='text' value='message'> | <input type='text' value='message' name='value'> | Add name attribute. | HTML |
#header {{ color: #fff; }} | #header {{ color: #fff; }} | Correct. | CSS |
data.forEach(function(a) {{ console.log(a); }}) | data.forEach((a) => {{ console.log(a); }}) | Arrow functions are cleaner. | JavaScript |
{{'status':'hello'}} | {{"status":"hello"}} | Use double quotes. | JSON |
let mut result=16; let ref1=&mut result; let r2=&mut result; | let mut result=16; {{ let ref1=&mut result; }} let r2=&mut result; | Only one mutable borrow. | Rust |
item = 1 | item=1 | No spaces. | Shell |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
[54, 51, 16 | [54, 51, 16] | Close bracket. | Python |
print('test') | print('test') | Correct. | R |
try:
x = 1 / 0
except
pass | try:
x = 1 / 0
except Exception:
pass | Specify exception type. | Python |
let str = String::from("hello"); let r=&str; str.push_str("!"); | let mut str = String::from("hello"); let r=&str; println!("{{}}", r); str.push_str("!"); | Cannot mutate while borrowed. | Rust |
<br></br> | <br> | Self-closing. | HTML |
for (item in values) | for (item of values) | for...in iterates keys. | JavaScript |
'21' + 28 | 21 + 28 | Avoid string coercion. | JavaScript |
if (bar = 95) {{}} | if (bar === 95) {{}} | Use === for equality. | JavaScript |
cin >> temp
cout << temp; | cin >> temp;
cout << temp; | Add semicolon. | C++ |
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