Add: Add Strings

Author: openset

problems/add-strings/add_strings.go

@@ -1 +1,20 @@
-package add_strings
+package problem_415
+
+func addStrings(num1 string, num2 string) string {
+	ans, l1, l2, carry := "", len(num1)-1, len(num2)-1, byte('0')
+	for l1 >= 0 || l2 >= 0 || carry != '0' {
+		v := carry
+		if l1 >= 0 {
+			v += num1[l1] - '0'
+			l1--
+		}
+		if l2 >= 0 {
+			v += num2[l2] - '0'
+			l2--
+		}
+		carry = '0' + (v-'0')/10
+		v = '0' + (v-'0')%10
+		ans = string(v) + ans
+	}
+	return ans
+}

problems/add-strings/add_strings_test.go

@@ -1 +1,40 @@
-package add_strings
+package problem_415
+
+import "testing"
+
+type caseType struct {
+	num1     string
+	num2     string
+	expected string
+}
+
+func TestAddStrings(t *testing.T) {
+	tests := [...]caseType{
+		{
+			num1:     "0",
+			num2:     "0",
+			expected: "0",
+		},
+		{
+			num1:     "1",
+			num2:     "2",
+			expected: "3",
+		},
+		{
+			num1:     "9",
+			num2:     "9",
+			expected: "18",
+		},
+		{
+			num1:     "100",
+			num2:     "999",
+			expected: "1099",
+		},
+	}
+	for _, tc := range tests {
+		output := addStrings(tc.num1, tc.num2)
+		if output != tc.expected {
+			t.Fatalf("input: %v, output: %v, expected: %v", tc, output, tc.expected)
+		}
+	}
+}