# Difference between revisions of "Euler problems/161 to 170"

From HaskellWiki

(Added problem_164) |
(Added solution for problem 166) |
||

Line 47: | Line 47: | ||

Solution: |
Solution: |
||

<haskell> |
<haskell> |
||

− | problem_166 = |
+ | problem_166 = |

+ | sum [ product (map count [[0, c, b-d, a-b-d], |
||

+ | [0, b-a, c+d-a, b+d-a], |
||

+ | [0, -b-c, a-b-c-d, -c-d], |
||

+ | [0, a, d, c+d]])| |
||

+ | a <- [-9..9], |
||

+ | b <- [-9+a..9+a], |
||

+ | c <- [-9..9], |
||

+ | d <- [-9+a-c..9+a-c]] |
||

+ | where |
||

+ | count xs |
||

+ | |u<l=0 |
||

+ | |otherwise=u-l+1 |
||

+ | where |
||

+ | l = -minimum xs |
||

+ | u = 9-maximum xs |
||

</haskell> |
</haskell> |
||

Line 56: | Line 56: | ||

<haskell> |
<haskell> |
||

problem_167 = undefined |
problem_167 = undefined |
||

+ | </haskell> |
||

+ | |||

+ | == [http://projecteuler.net/index.php?section=view&id=168 Problem 168] == |
||

+ | Number Rotations |
||

+ | |||

+ | Solution: |
||

+ | <haskell> |
||

+ | problem_168 = undefined |
||

+ | </haskell> |
||

+ | |||

+ | == [http://projecteuler.net/index.php?section=view&id=169 Problem 169] == |
||

+ | Exploring the number of different ways a number can be expressed as a sum of powers of 2. |
||

+ | |||

+ | Solution: |
||

+ | <haskell> |
||

+ | problem_169 = undefined |
||

+ | </haskell> |
||

+ | |||

+ | == [http://projecteuler.net/index.php?section=view&id=170 Problem 170] == |
||

+ | Find the largest 0 to 9 pandigital that can be formed by concatenating products. |
||

+ | |||

+ | Solution: |
||

+ | <haskell> |
||

+ | problem_170 = undefined |
||

</haskell> |
</haskell> |

## Revision as of 05:30, 21 January 2008

## Contents

## Problem 161

Triominoes

Solution:

```
problem_161 = undefined
```

## Problem 162

Hexadecimal numbers

Solution:

```
problem_162 = undefined
```

## Problem 163

Cross-hatched triangles

Solution:

```
problem_163 = undefined
```

## Problem 164

Numbers for which no three consecutive digits have a sum greater than a given value.

Solution:

```
addDigit x = [[sum [x !! b !! c | c <- [0..9-a-b]] | b <- [0..9-a]] | a<-[0..9]]
x3 = [[10-a-b | b <- [0..9-a]] | a <- [0..9]]
x20 = iterate addDigit x3 !! 17
problem_164 = sum [x20 !! a !! b | a <- [1..9], b <- [0..9-a]]
```

## Problem 165

Intersections

Solution:

```
problem_165 = undefined
```

## Problem 166

Criss Cross

Solution:

```
problem_166 =
sum [ product (map count [[0, c, b-d, a-b-d],
[0, b-a, c+d-a, b+d-a],
[0, -b-c, a-b-c-d, -c-d],
[0, a, d, c+d]])|
a <- [-9..9],
b <- [-9+a..9+a],
c <- [-9..9],
d <- [-9+a-c..9+a-c]]
where
count xs
|u<l=0
|otherwise=u-l+1
where
l = -minimum xs
u = 9-maximum xs
```

## Problem 167

Investigating Ulam sequences

Solution:

```
problem_167 = undefined
```

## Problem 168

Number Rotations

Solution:

```
problem_168 = undefined
```

## Problem 169

Exploring the number of different ways a number can be expressed as a sum of powers of 2.

Solution:

```
problem_169 = undefined
```

## Problem 170

Find the largest 0 to 9 pandigital that can be formed by concatenating products.

Solution:

```
problem_170 = undefined
```