28 lines
537 B
C
28 lines
537 B
C
// Try to use recursion to solve this problem.
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#include <stdio.h>
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// function prototypes.
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unsigned long long int sum(unsigned long long int n);
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int main(void) {
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// Initialize variables and get input from user.
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unsigned long long int num;
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scanf("%lld", &num);
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// Print values
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printf("%lld\n", sum(num));
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return 0;
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}
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unsigned long long int sum(unsigned long long int n) {
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if (n == 1 || n == 2) { // Case 1: n is 1 or 2
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return 0;
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} else { // Case 2: n is not
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return n * (n - 1) * (n - 2) + sum(n - 1);
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}
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}
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