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day 2 solution. both with division and without
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package day2 | ||
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// ProductsExceptI returns an array with the products of all numbers | ||
// except the value at the i-th position. | ||
// O(N) time complexity. | ||
// O(1) space complexity. | ||
func ProductsExceptI(arr []int) []int { | ||
result := make([]int, len(arr)) | ||
total := 1 | ||
for _, v := range arr { | ||
total *= v | ||
} | ||
for i, v := range arr { | ||
result[i] = total / v | ||
} | ||
return result | ||
} | ||
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// ProductsExceptINoDivision returns an array with the products of all numbers | ||
// except the value at the i-th position. Without using division. | ||
// O(N^2) time complexity. | ||
// O(1) space complexity. | ||
func ProductsExceptINoDivision(arr []int) []int { | ||
result := make([]int, len(arr)) | ||
for i := range arr { | ||
total := 1 | ||
for j, w := range arr { | ||
if i != j { | ||
total *= w | ||
} | ||
} | ||
result[i] = total | ||
} | ||
return result | ||
} |
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package day2 | ||
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import ( | ||
"reflect" | ||
"testing" | ||
) | ||
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var testcases = []struct { | ||
input, expected []int | ||
}{ | ||
{[]int{1, 2, 3, 4, 5}, []int{120, 60, 40, 30, 24}}, | ||
{[]int{3, 2, 1}, []int{2, 3, 6}}, | ||
} | ||
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func TestProductsExceptI(t *testing.T) { | ||
t.Run("ProductsExceptI", func(t *testing.T) { | ||
t.Parallel() | ||
for _, tc := range testcases { | ||
if result := ProductsExceptI(tc.input); !reflect.DeepEqual(result, tc.expected) { | ||
t.Error("didn't get what I expected") | ||
} | ||
} | ||
}) | ||
t.Run("ProductsExceptINoDivision", func(t *testing.T) { | ||
t.Parallel() | ||
for _, tc := range testcases { | ||
if result := ProductsExceptINoDivision(tc.input); !reflect.DeepEqual(result, tc.expected) { | ||
t.Error("didn't get what I expected") | ||
} | ||
} | ||
}) | ||
} | ||
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func BenchmarkProductsExceptI(b *testing.B) { | ||
b.Run("ProductsExceptI", func(b *testing.B) { | ||
for i := 0; i < b.N; i++ { | ||
for _, tc := range testcases { | ||
ProductsExceptI(tc.input) | ||
} | ||
} | ||
}) | ||
b.Run("ProductsExceptINoDivision", func(b *testing.B) { | ||
for i := 0; i < b.N; i++ { | ||
for _, tc := range testcases { | ||
ProductsExceptI(tc.input) | ||
} | ||
} | ||
}) | ||
} |