문제
Every neuron starts with the same calculation: multiply each input by its weight and add everything up. That is the dot product of two vectors:
a · b = a₁×b₁ + a₂×b₂ + … + aₙ×bₙ
Implement dot_product(a, b).
Input
a, b: Two lists of numbers with the same length.
Output
Return the dot product as a decimal number.
제약 조건
1 ≤ length of a = length of b ≤ 1,000
-1,000 ≤ each value ≤ 1,000
예시
입력:
a = [1.0, 2.0, 3.0]
b = [4.0, 5.0, 6.0]
예상 출력:
expected = 32.0입력:
std::vector<double> a = {1.0, 2.0, 3.0};
std::vector<double> b = {4.0, 5.0, 6.0};
예상 출력:
double expected = 32.0;입력:
double[] a = new double[] {1.0, 2.0, 3.0};
double[] b = new double[] {4.0, 5.0, 6.0};
예상 출력:
double expected = 32.0;설명
1×4 + 2×5 + 3×6 = 4 + 10 + 18 = 32.
입력:
a = [0.5, -1.5]
b = [2.0, 4.0]
예상 출력:
expected = -5.0입력:
std::vector<double> a = {0.5, -1.5};
std::vector<double> b = {2.0, 4.0};
예상 출력:
double expected = -5.0;입력:
double[] a = new double[] {0.5, -1.5};
double[] b = new double[] {2.0, 4.0};
예상 출력:
double expected = -5.0;설명
0.5×2 + (-1.5)×4 = 1 - 6 = -5.
접근 방법
먼저 스스로 풀어 본 뒤 힌트를 하나씩 열어 보세요.
힌트 1
Multiply matching positions from the two lists and combine the results into one total.
힌트 2
A single pass is enough because each pair contributes independently to the final value.
힌트 3
Make sure the lists have the same length, and keep the accumulator in a numeric type that preserves decimals if needed.
예상 복잡도
O(n) time, O(1) extra space
참고 자료
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