問題
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.
制約
1 ≤ length of a = length of b ≤ 1,000
-1,000 ≤ each value ≤ 1,000
例
入力：
a = [1.0, 2.0, 3.0]
b = [4.0, 5.0, 6.0]
期待される出力：
expected = 32.0入力：
std::vector<double> a = {1.0, 2.0, 3.0};
std::vector<double> b = {4.0, 5.0, 6.0};
期待される出力：
double expected = 32.0;入力：
double[] a = new double[] {1.0, 2.0, 3.0};
double[] b = new double[] {4.0, 5.0, 6.0};
期待される出力：
double expected = 32.0;解説
1×4 + 2×5 + 3×6 = 4 + 10 + 18 = 32.
入力：
a = [0.5, -1.5]
b = [2.0, 4.0]
期待される出力：
expected = -5.0入力：
std::vector<double> a = {0.5, -1.5};
std::vector<double> b = {2.0, 4.0};
期待される出力：
double expected = -5.0;入力：
double[] a = new double[] {0.5, -1.5};
double[] b = new double[] {2.0, 4.0};
期待される出力：
double expected = -5.0;解説
0.5×2 + (-1.5)×4 = 1 - 6 = -5.
解き方のヒント
まずは自分で考えてから、ヒントを 1 つずつ開いてみましょう。
ヒント 1
Multiply matching positions from the two lists and combine the results into one total.
ヒント 2
A single pass is enough because each pair contributes independently to the final value.
ヒント 3
Make sure the lists have the same length, and keep the accumulator in a numeric type that preserves decimals if needed.
目安の計算量
O(n) time, O(1) extra space
参考資料
この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。