Euler problems/141 to 150
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1 Problem 141
Investigating progressive numbers, n, which are also square.
Solution:
problem_141 = undefined
2 Problem 142
Perfect Square Collection
Solution:
import List isSquare n = (round . sqrt $ fromIntegral n) ^ 2 == n aToX (a,b,c)=[x,y,z] where x=div (a+b) 2 y=div (a-b) 2 z=c-x {- - 2 2 2 - a = c + d - 2 2 2 - a = e + f - 2 2 2 - c = e + b - let b=x*y then - (y + xb) - c= --------- - 2 - (-y + xb) - e= --------- - 2 - (-x + yb) - d= --------- - 2 - (x + yb) - f= --------- - 2 - - and - 2 2 2 - a = c + d - then - 2 2 2 2 - 2 (y + x ) (x y + 1) - a = --------------------- - 4 - -} problem_142 = sum$head[aToX(t,t2 ,t3)| a<-[3,5..50], b<-[(a+2),(a+4)..50], let a2=a^2, let b2=b^2, let n=(a2+b2)*(a2*b2+1), isSquare n, let t=div n 4, let t2=a2*b2, let t3=div (a2*(b2+1)^2) 4 ]
3 Problem 143
Investigating the Torricelli point of a triangle
Solution:
problem_143 = undefined
4 Problem 144
Investigating multiple reflections of a laser beam.
Solution:
problem_144 = undefined
5 Problem 145
How many reversible numbers are there below one-billion?
Solution:
import List digits n {- 123->[3,2,1] -} |n<10=[n] |otherwise= y:digits x where (x,y)=divMod n 10 -- 123 ->321 dmm=(\x y->x*10+y) palind n=foldl dmm 0 (digits n) isOdd x=(length$takeWhile odd x)==(length x) isOdig x=isOdd m && s<=h where k=x+palind x m=digits k y=floor$logBase 10 $fromInteger x ten=10^y s=mod x 10 h=div x ten a2=[i|i<-[10..99],isOdig i] aa2=[i|i<-[10..99],isOdig i,mod i 10/=0] a3=[i|i<-[100..999],isOdig i] m5=[i|i1<-[0..99],i2<-[0..99], let i3=i1*1000+3*100+i2, let i=10^6* 8+i3*10+5, isOdig i ] fun i |i==2 =2*le aa2 |even i=(fun 2)*d^(m-1) |i==3 =2*le a3 |i==7 =fun 3*le m5 |otherwise=0 where le=length m=div i 2 d=2*le a2 problem_145 = sum[fun a|a<-[1..9]]
6 Problem 146
Investigating a Prime Pattern
Solution:
problem_146 = undefined
7 Problem 147
Rectangles in cross-hatched grids
Solution:
problem_147 = undefined
8 Problem 148
Exploring Pascal's triangle.
Solution:
problem_148 = undefined
9 Problem 149
Searching for a maximum-sum subsequence.
Solution:
problem_149 = undefined
10 Problem 150
Searching a triangular array for a sub-triangle having minimum-sum.
Solution:
problem_150 = undefined
