我正在尝试编写编程挑战书籍中的第一个问题。该代码计算从 a 到 b 生成的数字的数量。
如果 n 为偶数，则新的 n 为 n/2，如果为奇数，则为 3*n+1
例如，对于 22，它将计算数字 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1 等等数字是 16。打印 113383 后代码停止，我输入为
1 1000000
#include <iostream>
#include <map>
#include <vector>
using std::cout;
using std::cin;
using std::string;
using std::endl;
using std::vector;
using std::map;
map<long,long> solution;
long sequences(long n) {
// returns the number of numbers(including 1) `n`produces till it becomes 1
if(n==1)
return 1;
else{
// assuming n>1
if(solution.find(n)!=solution.end())
return solution.find(n)->second;
long size = 0;
while(n!=1){
if(n%2==0){
n = n/2;
if(solution.find(n)!=solution.end())
return solution.find(n)->second + size;
}
else{
n = 3*n+1;
}
size++;
}
return size+1;
}
}
long sequences(long a,long b){
// returns the maximum numbers produced by numbers from a to b inclusive
long result,max = -1;
if(a<b){
for(long i=a;i<=b;i=i+1){
if(solution.find(i) == solution.end()){
cout<< i << endl;
result = sequences(i);
solution.insert(map<long,long>::value_type(i,result));
}
else{
//i present in solution
result = solution.find(i)->second;
}
if(result>max)
max = result;
}
return max;
}
return -1;
}
int main(int argc, char* argv[]) {
long a,b,max;
cin >> a >> b;
// while(cin>>a>>b){
cout<<a<<" "<<b<<" "<<sequences(a,b)<<endl;
/*}*/
return 0;
}