One, Two, Three Plus Four
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Count the number of unordered sums of 1, 2, and 3 that add up to a given n, for each test case.
- Level
Medium4 of 10
- Topics
- Dynamic programming, Combinatorics, Math, Implementation
- Solved
- No attempts yet
Problem
There are 4 ways to express the integer 4 as a sum of 1, 2, and 3. A sum must use at least one number. Two sums that differ only in the order of their terms count as the same way.
- 1+1+1+1
- 2+1+1 (1+1+2, 1+2+1)
- 2+2
- 1+3 (3+1)
Given an integer n, write a program that finds the number of ways to express n as a sum of 1, 2, and 3.
Input
The first line gives the number of test cases T. Each test case consists of one line and gives an integer n. n is a positive integer and is at most 10,000.
Output
For each test case, print the number of ways to express n as a sum of 1, 2, and 3.