golang leetcode 30天挑戰 10th day -subtract-the-product-and-sum-of-digits-of-an-integer

題目解讀：

題目來源:

subtract-the-product-and-sum-of-digits-of-an-integer

原文:

Given an integer number n, return the difference between the product of its digits and the sum of its digits.

解讀：

給定一個正整數 n

回傳 n的每個digit相乘 減去 n的每個digit相加的結果

舉例來說:

n = 234

f(n) => 2 * 3 * 4 - 2+3+4= 24 - 9 =15

初步解法:

初步觀察:

首先是每個digit取得可以透過 %10得到的結果

然後在用/10 去shift到下一個digit

n = 234 => check n > 0 , n % 10 = 4, n /= 10
n = 23 => check n > 0 , n % 10 = 3, n /= 10
n = 2 => check n > 0, n % 10 = 2, n /= 10
n = 0

初步設計:

given an integer n

step 0: let a integer sum = 0, a integer product = 1

step 1: if n <= 0 go to step 3

step 2: sum += n%10, product*= n%10, n/=10, go to step1

step 3: return product - sum

my solution source code

subtractProductAndSum.go

package subtract_product_sum

func subtractProductAndSum(n int) int {
	sum := 0
	product := 1
	for n > 0 {
		digit := n % 10
		sum += digit
		product *= digit
		n /= 10
	}
	return product - sum
}

遇到的困難

題目上理解的問題

因為英文不是筆者母語

所以在題意解讀上 容易被英文用詞解讀給搞模糊

pseudo code撰寫

一開始不習慣把pseudo code寫下來

因此 不太容易把自己的code做解析

golang table driven test不熟

對於table driven test還不太熟析

所以對於寫test還是耗費不少時間

測資的撰寫

package subtract_product_sum

import "testing"

func Test_subtractProductAndSum(t *testing.T) {
	type args struct {
		n int
	}
	tests := []struct {
		name string
		args args
		want int
	}{
		{
			name: "Example1",
			args: args{
				n: 234,
			},
			want: 15,
		},
		{
			name: "Example2",
			args: args{
				n: 4421,
			},
			want: 21,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if got := subtractProductAndSum(tt.args.n); got != tt.want {
				t.Errorf("subtractProductAndSum() = %v, want %v", got, tt.want)
			}
		})
	}
}

參考文章

golang test