70 lines
1.7 KiB
C++
70 lines
1.7 KiB
C++
#include <iostream>
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#include "timing.h"
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using namespace std;
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unsigned long multiplesOf3Or5(unsigned int n)
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{
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unsigned long sum = 0;
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for(unsigned int i=1; i<=n; i++)
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{
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if(i % 3 == 0 || i % 5 == 0)
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{
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sum += i;
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}
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}
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return sum;
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}
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unsigned long gauss_sum(unsigned long n)
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{
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return n*(n+1)/2;
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}
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unsigned long multiplesOf3Or5_noLoop(unsigned int n)
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{
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/*for n there are floor(n/3) multiples of 3 and floor(n/5) multiples of 5. Calculate them using Gauss summation and subtract the
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multiples of 15 (counted twice)*/
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unsigned long multiples3 = gauss_sum(n/3)*3;
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unsigned long multiples5 = gauss_sum(n/5)*5;
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unsigned long multiples15 = gauss_sum(n/15)*15;
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return multiples3 + multiples5 - multiples15;
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}
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int main() {
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unsigned long mA,mB,mC,mD,mE,mF;
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tic();
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for(unsigned int i = 0; i< 10000; i++)
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{
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mA = multiplesOf3Or5(15);
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mB = multiplesOf3Or5(1001);
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mC = multiplesOf3Or5(1432987);
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}
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double timeA = toc();
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tic();
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for(unsigned int i = 0; i< 10000; i++)
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{
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mD = multiplesOf3Or5_noLoop(15);
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mE = multiplesOf3Or5_noLoop(1001);
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mF = multiplesOf3Or5_noLoop(1432987);
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}
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double timeB = toc();
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cout << "n = 15, result = " << mA << endl;
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cout << "n = 1001, result = " << mB << endl;
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cout << "n = 1432987, result = " << mC << endl;
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cout << "time: " << timeA << endl;
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cout << "--------------------------------------------------------------" <<endl;
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cout << "n = 15, result = " << mD << endl;
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cout << "n = 1001, result = " << mE << endl;
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cout << "n = 1432987, result = " << mF << endl;
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cout << "time: " << timeB << endl;
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return 0;
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}
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