52 lines
1.2 KiB
Dart
52 lines
1.2 KiB
Dart
List<int> hailstone(int n) {
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if(n<=0) {
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throw new IllegalArgumentException("start value must be >=1)");
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}
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Queue<int> seq=new Queue<int>();
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seq.add(n);
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while(n!=1) {
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n=n%2==0?(n/2).toInt():3*n+1;
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seq.add(n);
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}
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return new List<int>.from(seq);
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}
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// apparently List is missing toString()
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String iterableToString(Iterable seq) {
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String str="[";
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Iterator i=seq.iterator();
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while(i.hasNext()) {
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str+=i.next();
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if(i.hasNext()) {
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str+=",";
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}
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}
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return str+"]";
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}
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main() {
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for(int i=1;i<=10;i++) {
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print("h($i)="+iterableToString(hailstone(i)));
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}
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List<int> h27=hailstone(27);
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List<int> first4=h27.getRange(0,4);
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print("first 4 elements of h(27): "+iterableToString(first4));
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Expect.listEquals([27,82,41,124],first4);
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List<int> last4=h27.getRange(h27.length-4,4);
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print("last 4 elements of h(27): "+iterableToString(last4));
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Expect.listEquals([8,4,2,1],last4);
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print("length of sequence h(27): "+h27.length);
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Expect.equals(112,h27.length);
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int seq,max=0;
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for(int i=1;i<=100000;i++) {
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List<int> h=hailstone(i);
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if(h.length>max) {
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max=h.length;
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seq=i;
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}
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}
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print("up to 100000 the sequence h($seq) has the largest length ($max)");
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}
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