feat: Add isSubsequence string algorithm (#684)

strings/issubsequence.go

@@ -0,0 +1,35 @@
+// Checks if a given string is a subsequence of another string.
+// A subsequence of a given string is a string that can be derived from the given
+// string by deleting some or no characters without changing the order of the
+// remaining characters. (i.e., "dpr" is a subsequence of "depqr" while "drp" is not).
+// Author: sanjibgirics
+
+package strings
+
+// Returns true if s is subsequence of t, otherwise return false.
+func IsSubsequence(s string, t string) bool {
+	if len(s) > len(t) {
+		return false
+	}
+
+	if s == t {
+		return true
+	}
+
+	if len(s) == 0 {
+		return true
+	}
+
+	sIndex := 0
+	for tIndex := 0; tIndex < len(t); tIndex++ {
+		if s[sIndex] == t[tIndex] {
+			sIndex++
+		}
+
+		if sIndex == len(s) {
+			return true
+		}
+	}
+
+	return false
+}

strings/issubsequence_test.go

@@ -0,0 +1,75 @@
+package strings_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/TheAlgorithms/Go/strings"
+)
+
+func TestIsSubsequence(t *testing.T) {
+	var testCases = []struct {
+		name     string
+		s        string
+		t        string
+		expected bool
+	}{
+		{
+			"Valid case 1 ",
+			"ace",
+			"abcde",
+			true,
+		},
+		{
+			"Invalid case 1",
+			"aec",
+			"abcde",
+			false,
+		},
+		{
+			"Empty strings",
+			"",
+			"",
+			true,
+		},
+		{
+			"s is more then t",
+			"aeccccc",
+			"abcde",
+			false,
+		},
+		{
+			"s is empty",
+			"",
+			"abcde",
+			true,
+		},
+		{
+			"Equal strings",
+			"aec",
+			"aec",
+			true,
+		},
+		{
+			"Valid case 2",
+			"pyr",
+			"wpxqyrz",
+			true,
+		},
+		{
+			"Invalid case 2",
+			"prx",
+			"wpxqyrz",
+			false,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			funcResult := strings.IsSubsequence(test.s, test.t)
+			if !reflect.DeepEqual(test.expected, funcResult) {
+				t.Errorf("expected: %v, got %v", test.expected, funcResult)
+			}
+		})
+	}
+}