53 lines
1.0 KiB
C++
53 lines
1.0 KiB
C++
/** The Fibonacci sequence is defined by the recurrence relation:
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Fn = Fn1 + Fn2, where F1 = 1 and F2 = 1.
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Hence the first 12 terms will be:
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F1 = 1
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F2 = 1
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F3 = 2
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F4 = 3
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F5 = 5
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F6 = 8
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F7 = 13
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F8 = 21
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F9 = 34
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F10 = 55
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F11 = 89
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F12 = 144
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The 12th term, F12, is the first term to contain three digits.
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What is the first term in the Fibonacci sequence to contain 1000 digits? */
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#include "0.hpp"
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#include "lib/lint.cpp"
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void fib_matrix(unsigned int maxnum);
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int main()
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{
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unsigned int max;
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cin >> max;
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//for(int i = 1; i <= max; i++) cout << fib_recursive(i) << endl;
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fib_matrix(max);
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return 0;
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}
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void fib_matrix(unsigned int maxnum)
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{
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string first = "1";
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lint fib[2];
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fib[0] = first;
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fib[1] = first;
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//for(int i = 1; i <= maxnum; i++) {
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int i = 1;
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while(1) {
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//cout << fib[i % 2].getd() << endl;
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if(fib[i % 2].getd().size() >= maxnum) break;
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if(i >= 2) fib[(i + 1) % 2] = fib[(i + 1) % 2] + fib[i % 2];
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i++;
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}
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//cout << fib[maxnum % 2].getd() << endl;
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cout << i << endl;
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}
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