probleme_26.groovy

// An offset defining a kind of header we don't want to see as it pollutes computations
// Yup, it's a hack
def OFFSET = 1000
def SCANNED_SIZE = 10000
def UPSCALE = SCANNED_SIZE+OFFSET
def MAX = 1000


long start = System.currentTimeMillis();

// detector regexp pattern
def detector = ~/([0-9]*)\1+.*/
def initial = 1g
initial = initial.toBigDecimal()
def scale = initial.scale()+UPSCALE
def matchings = [:]
for(n in 1..MAX) {
	if(n%2!=0) {
		if((n+1)%100==0) {
			println "scanning $n"
		}
		def decimals = initial.divide(n, scale, java.math.RoundingMode.HALF_EVEN)
		def decimalsStr = "$decimals"
		def initialDecimals = decimalsStr = decimalsStr.substring(OFFSET)
		// fight pattern and string and as long as it matches, repeat operation
		def matcher = detector.matcher(decimalsStr)
		for(; matcher.matches() && matcher[0][1].size()>0 && decimalsStr.size()>1; matcher =detector.matcher(decimalsStr)) {
			decimalsStr = matcher[0][1]
		}
		matchings[n]=decimalsStr
	}
}
greatest = matchings.max {a, b -> a.value.size() <=> b.value.size() }
println "${greatest.key} has cycle of ${greatest.value.size()} length"


long end = System.currentTimeMillis();
println "duration "+((end-start)/1000.0)+" s";