add solution interger to english words

Author: freefcw

go/integer-to-english-words.go

@@ -0,0 +1,88 @@
+package leetcode
+
+var (
+	nwTens = []string{"Zero", "Ten", "Twenty", "Thirty", "Forty",
+		"Fifty", "Sixty", "Seventy", "Eighty", "Ninety"}
+	nwBasic = []string{"Zero", "One", "Two", "Three", "Four",
+		"Five", "Six", "Seven", "Eight", "Nine", "Ten",
+		"Eleven", "Twelve", "Thirteen", "Fourteen",
+		"Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"}
+)
+
+func simpleNumberToWords(num int) string {
+	hundred := 0
+	result := ""
+	if num > 99 {
+		hundred = num / 100
+		result = nwBasic[hundred] + " " + "Hundred"
+	}
+	num = num - hundred*100
+	if num > 19 {
+		tens := num / 10
+		left := num % 10
+		if left != 0 {
+			if len(result) != 0 {
+				result = result + " " + nwTens[tens] + " " + nwBasic[left]
+			} else {
+				result = nwTens[tens] + " " + nwBasic[left]
+			}
+		} else {
+			if len(result) != 0 {
+				result = result + " " + nwTens[tens]
+			} else {
+				result = nwTens[tens]
+			}
+		}
+	} else {
+		if num != 0 {
+			if result != "" {
+				result = result + " " + nwBasic[num]
+			} else {
+				result = nwBasic[num]
+			}
+
+		}
+	}
+
+	return result
+}
+
+func numberToWords(num int) string {
+	if num == 0 {
+		return "Zero"
+	}
+	result := ""
+	if num > (1000000000 - 1) {
+		current := num / 1000000000
+		result = simpleNumberToWords(current) + " " + "Billion"
+		num = num % 1000000000
+	}
+	if num > (1000000 - 1) {
+		current := num / 1000000
+		if result != "" {
+			result = result + " " + simpleNumberToWords(current) + " " + "Million"
+		} else {
+			result = simpleNumberToWords(current) + " " + "Million"
+		}
+
+		num = num % 1000000
+	}
+	if num > (1000 - 1) {
+		current := num / 1000
+		if result != "" {
+			result = result + " " + simpleNumberToWords(current) + " " + "Thousand"
+		} else {
+			result = simpleNumberToWords(current) + " " + "Thousand"
+		}
+		num = num % 1000
+	}
+	if result != "" {
+		if num != 0 {
+			result = result + " " + simpleNumberToWords(num)
+		}
+	} else {
+		result = simpleNumberToWords(num)
+	}
+
+	return result
+}

go/integer-to-english-words_test.go

@@ -0,0 +1,104 @@
+package leetcode
+
+import "testing"
+
+func TestSimpleNumberToWords(t *testing.T) {
+	tests := []struct {
+		input  int
+		expect string
+	}{
+		{
+			input:  0,
+			expect: "",
+		}, {
+			input:  1,
+			expect: "One",
+		}, {
+			input:  19,
+			expect: "Nineteen",
+		}, {
+			input:  10,
+			expect: "Ten",
+		}, {
+			input:  20,
+			expect: "Twenty",
+		}, {
+			input:  21,
+			expect: "Twenty One",
+		}, {
+			input:  29,
+			expect: "Twenty Nine",
+		}, {
+			input:  99,
+			expect: "Ninety Nine",
+		}, {
+			input:  100,
+			expect: "One Hundred",
+		}, {
+			input:  123,
+			expect: "One Hundred Twenty Three",
+		}, {
+			input:  120,
+			expect: "One Hundred Twenty",
+		}, {
+			input:  201,
+			expect: "Two Hundred One",
+		}, {
+			input:  999,
+			expect: "Nine Hundred Ninety Nine",
+		},
+	}
+
+	for _, item := range tests {
+		actual := simpleNumberToWords(item.input)
+		if actual != item.expect {
+			t.Fatalf("%d expect %s, actual %s\n", item.input, item.expect, actual)
+		}
+	}
+}
+
+func TestNumberToWords(t *testing.T) {
+	tests := []struct {
+		input  int
+		expect string
+	}{
+		{
+			input:  0,
+			expect: "Zero",
+		}, {
+			input:  1,
+			expect: "One",
+		}, {
+			input:  20,
+			expect: "Twenty",
+		}, {
+			input:  120,
+			expect: "One Hundred Twenty",
+		}, {
+			input:  999,
+			expect: "Nine Hundred Ninety Nine",
+		}, {
+			input:  1000,
+			expect: "One Thousand",
+		}, {
+			input:  12345,
+			expect: "Twelve Thousand Three Hundred Forty Five",
+		}, {
+			input:  1000000,
+			expect: "One Million",
+		}, {
+			input:  1234567,
+			expect: "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven",
+		}, {
+			input:  1234567891,
+			expect: "One Billion Two Hundred Thirty Four Million Five Hundred Sixty Seven Thousand Eight Hundred Ninety One",
+		},
+	}
+
+	for _, item := range tests {
+		actual := numberToWords(item.input)
+		if actual != item.expect {
+			t.Fatalf("%d expect %s, actual %s\n", item.input, item.expect, actual)
+		}
+	}
+}