65 lines
No EOL
1.3 KiB
C
Executable file
65 lines
No EOL
1.3 KiB
C
Executable file
#include <stdio.h>
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// The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:
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// 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
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// Let us list the factors of the first seven triangle numbers:
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// 1: 1
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// 3: 1,3
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// 6: 1,2,3,6
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// 10: 1,2,5,10
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// 15: 1,3,5,15
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// 21: 1,3,7,21
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// 28: 1,2,4,7,14,28
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// We can see that 28 is the first triangle number to have over five divisors.
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// What is the value of the first triangle number to have over five hundred divisors?
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//first attempt 29 minutes, 40 seconds
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//second attempt: 13 minutes, 32 seconds
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int countDivisors(long long);
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int main() {
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int i = 1;
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int j;
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long long triNumber;
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while(1) {
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if(i % 500 == 0) {
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printf("On iteration %d: \n", i);
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}
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//find the current tri number
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triNumber = ((i + 1) * i) / 2;
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i++;
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if(triNumber % 2 == 1) continue;
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int divisors = countDivisors(triNumber);
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if(divisors > 200) {
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printf("%lld (%d divisors)\n", triNumber, divisors);
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}
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if(divisors > 500) break;
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if(i < 0) break;
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}
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printf("\n%lld", triNumber);
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return 1;
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}
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int countDivisors(long long number) {
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int i;
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int divisors = 0;
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for(i = 1; i * 2 <= number; i++) {
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if(number % i == 0) {
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divisors++;
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}
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}
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return divisors + 1;
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} |