Calculate the Nth term HackerRank Solution
This challenge will help you learn the concept of recursion.
A function that calls itself is known as a recursive function. The C programming language supports recursion. But while using recursion, one needs to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
To prevent infinite recursion, if….else statement (or similar approach) can be used where one branch makes the recursive call and other doesn’t.
void recurse() {
.....
recurse() //recursive call
.....
}
int main() {
.....
recurse(); //function call
.....
}
Task
There is a series, S, where the next term is the sum of previous three terms. Given the first three terms of the series, a, b, and c respectively, you have to output the nth term of the series using recursion.
Input Format
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The first line contains a single integer, n.
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The next line contains 3 space-separated integers, a, b, and c.
Constraints
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1 <=n <= 20
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1 <= a,b,c <= 100
Output Format
Print the nth term of the series, S(n).
Sample Input 0
5
1 2 3
Sample Output 0
11
Explanation 0
Consider the following steps:
S(1) = 1
S(2) = 2
S(3) = 3
S(4) = S(3) + S(2) +S(1)
S(5) = S(4) + S(3) + S(2)
From steps 1, 2, 3, and 4, we can say S(4) = 3 + 2 + 1 = 6; then using the values from step 2, 3, 4, and 5, we get S(5) = 6 + 3 + 2 = 11. Thus, we print 11 as our answer.
Solution
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
//Complete the following function.
int find_nth_term(int n, int a, int b, int c) {
int term, t1 = a, t2 = b, t3 = c;
if (n == 1)
term = t1;
else if (n == 2)
term = t2;
else if (n == 3)
term = t3;
else {
for (int i = 4; i <= n; i++) {
term = t1 + t2 + t3;
t1 = t2;
t2 = t3;
t3 = term;
}
}
return term;
}
int main() {
int n, a, b, c;
scanf("%d %d %d %d", &n, &a, &b, &c);
int ans = find_nth_term(n, a, b, c);
printf("%d", ans);
return 0;
}
Steps used in solving the problem -
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First we have imported required header files.
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Then, we created the main function. It takes four arguments n specifies the term to find and a, b, and c, are the first three terms of the sequence.
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Then, we used some if conditions to handle the base cases. we also used an else condition to handle the case where n is greater than 3.
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At last, we used return statement to return the nth term of the sequence.
