### Part 2

Script

```dataweave
import countBy from dw::core::Arrays
var p = read(payload, "application/csv", {header:false,separator:" "})
var a = p.column_0
var b = p.column_3
---
a map ((item) ->
(b countBy ($==item)) * item
) then sum($)
```

## 🔹 Day 2

### Part 1

Script

```dataweave
import every, countBy from dw::core::Arrays
var decreasing = "decreasing"
var increasing = "increasing"
---
((payload splitBy "\n") map (
(($ splitBy " ") reduce ((number, a=[]) ->
if (isEmpty(a)) a+{
prevNum: number,
operation: null,
isSafe: true
} else (a[-1].operation match {
case null -> a+{
prevNum: number,
operation: if (a[-1].prevNum-number > 0) decreasing else increasing,
isSafe: [1, 2, 3] contains abs(a[-1].prevNum - number)
}
case "$(decreasing)" -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (a[-1].prevNum - number)
}
else -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (number - a[-1].prevNum)
}
})
)).isSafe every $
)) countBy $
```

### Part 2

Horrible code. But I did what I had to do :(

Script

```dataweave
import every, countBy from dw::core::Arrays
var decreasing = "decreasing"
var increasing = "increasing"
var newp = ((payload splitBy "\n") map (
(($ splitBy " ") reduce ((number, a=[]) ->
if (isEmpty(a)) a+{
prevNum: number,
operation: null,
isSafe: true
} else (a[-1].operation match {
case null -> a+{
prevNum: number,
operation: if (a[-1].prevNum-number > 0) decreasing else increasing,
isSafe: [1, 2, 3] contains abs(a[-1].prevNum - number)
}
case "$(decreasing)" -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (a[-1].prevNum - number)
}
else -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (number - a[-1].prevNum)
}
})
))
))
var safeOnes = newp filter ((item) -> item.isSafe every $)
var unsafeOnes = newp -- safeOnes
fun getScenarios(data) = data map ($ reduce ((number, a=[]) ->
if (isEmpty(a)) a+{
prevNum: number,
operation: null,
isSafe: true
} else (a[-1].operation match {
case null -> a+{
prevNum: number,
operation: if (a[-1].prevNum-number > 0) decreasing else increasing,
isSafe: [1, 2, 3] contains abs(a[-1].prevNum - number)
}
case "$(decreasing)" -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (a[-1].prevNum - number)
}
else -> a+{
prevNum: number,
operation: a[-1].operation,
isSafe: [1, 2, 3] contains (number - a[-1].prevNum)
}
})
))
---
unsafeOnes map ((firstArray) ->
getScenarios(firstArray.prevNum map ((number, numIndex) ->
firstArray.prevNum filter ((item, index) -> index != numIndex)
)) filter ((item) -> item.isSafe every $)
) filter (!isEmpty($))
then sizeOf($)+sizeOf(safeOnes)
```

## 🔹 Day 3

### Part 1

Script

```dataweave
(flatten(payload scan /mul\(\d+,\d+\)/)) map do {
var nums = flatten($ scan /\d+/)
---
nums[0] * nums[1]
} then sum($)
```

### Part 2

Script

```dataweave
(payload scan /(mul|don't|do)\(\d*,?\d*\)/) reduce ((op, a={r:0,"do":true}) ->
op[0][0 to 2] match {
case "mul" -> do {
var nums = flatten(op[0] scan /\d+/)
var newR = a.r + ((nums[0] default 0) * (nums[1] default 0))
---
{
r: if (a."do") newR else a.r,
"do": a."do"
}
}
case "don" -> { r: a.r, "do": false }
else -> { r: a.r, "do": true }
}
) then $.r
```

## 🔹 Day 4

### Part 1

Script

```dataweave
var lines = payload splitBy "\n"
var XMAS = "XMAS"
fun getLetter(x:Number,y:Number) = if ((x<0) or (y<0)) "" else (lines[x][y] default "")
fun getStr(str:String,x:Number,y:Number) = if ((x<0) or (y<0)) "" else (str[x to y])
---
flatten
(lines map ((lineStr, lineidx) ->
(lineStr splitBy "") map ((letter, letteridx) ->
if (letter=="X") (
// right
(if (XMAS == getStr(lineStr,letteridx,letteridx+3)) 1 else 0)
// left
+ (if (XMAS == getStr(lineStr,letteridx,letteridx-3)) 1 else 0)
// down
+ (if (XMAS == (letter ++ getLetter(lineidx+1,letteridx) ++ getLetter(lineidx+2,letteridx) ++ getLetter(lineidx+3,letteridx))) 1 else 0)
// // up
+ (if (XMAS == (letter ++ getLetter(lineidx-1,letteridx) ++ getLetter(lineidx-2,letteridx) ++ getLetter(lineidx-3,letteridx))) 1 else 0)
// down-right
+ (if (XMAS == (letter ++ getLetter(lineidx+1,letteridx+1) ++ getLetter(lineidx+2,letteridx+2) ++ getLetter(lineidx+3,letteridx+3))) 1 else 0)
// down-left
+ (if (XMAS == (letter ++ getLetter(lineidx+1,letteridx-1) ++ getLetter(lineidx+2,letteridx-2) ++ getLetter(lineidx+3,letteridx-3))) 1 else 0)
// up-right
+ (if (XMAS == (letter ++ getLetter(lineidx-1,letteridx+1) ++ getLetter(lineidx-2,letteridx+2) ++ getLetter(lineidx-3,letteridx+3))) 1 else 0)
// up-left
+ (if (XMAS == (letter ++ getLetter(lineidx-1,letteridx-1) ++ getLetter(lineidx-2,letteridx-2) ++ getLetter(lineidx-3,letteridx-3))) 1 else 0)
)
else 0
)
)) then sum($)
```

### Part 2

Script

```dataweave
var lines = payload splitBy "\n"
fun getLetter(x:Number,y:Number) = if ((x<0) or (y<0)) "" else (lines[x][y] default "")
var xmas = ["MAS", "SAM"]
---
flatten
(lines map ((lineStr, lineidx) ->
(lineStr splitBy "") map ((letter, letteridx) ->
if (letter=="A") do {
var topleft = getLetter(lineidx-1, letteridx-1)
var topright = getLetter(lineidx-1, letteridx+1)
var bottomleft = getLetter(lineidx+1, letteridx-1)
var bottomright = getLetter(lineidx+1, letteridx+1)
var cross1 = topleft ++ letter ++ bottomright
var cross2 = topright ++ letter ++ bottomleft
---
if ( (xmas contains cross1) and (xmas contains cross2) ) 1 else 0
}
else 0
)
)) then sum($)
```