Add problem 91 - Decode Ways

Author: anirudhology

problems/dynamic_programming/decode_ways.go

@@ -0,0 +1,23 @@
+package dynamic_programming
+
+func DecodeWays(s string) int {
+	// Special case
+	if len(s) == 0 {
+		return 0
+	}
+	// Length of the string and previous and current pointers
+	n, previous, current := len(s), 1, 0
+	// Process the string from right to left
+	for i := n - 1; i >= 0; i-- {
+		temp := 0
+		if s[i] != '0' {
+			temp = previous
+		}
+		if i < n-1 && (s[i] == '1' || s[i] == '2' && s[i+1] < '7') {
+			temp += current
+		}
+		current = previous
+		previous = temp
+	}
+	return previous
+}

tests/dynamic_programming/decode_ways_test.go

@@ -0,0 +1,44 @@
+package dynamic_programming_test
+
+import (
+	"testing"
+
+	"github.com/anirudhology/leetcode-go/problems/dynamic_programming"
+)
+
+func TestNumDecodings(t *testing.T) {
+	// Test case for null string
+	if result := dynamic_programming.DecodeWays(""); result != 0 {
+		t.Errorf("Expected 0, got %d", result)
+	}
+
+	// Test case for string with a single character
+	if result := dynamic_programming.DecodeWays("1"); result != 1 {
+		t.Errorf("Expected 1, got %d", result)
+	}
+
+	// Test case for string with multiple characters
+	if result := dynamic_programming.DecodeWays("12"); result != 2 {
+		t.Errorf("Expected 2, got %d", result)
+	}
+
+	// Test case for string with leading zeros
+	if result := dynamic_programming.DecodeWays("012"); result != 0 {
+		t.Errorf("Expected 0, got %d", result)
+	}
+
+	// Test case for string with multiple decoding possibilities
+	if result := dynamic_programming.DecodeWays("226"); result != 3 {
+		t.Errorf("Expected 3, got %d", result)
+	}
+
+	// Test case for string with no valid decodings
+	if result := dynamic_programming.DecodeWays("30"); result != 0 {
+		t.Errorf("Expected 0, got %d", result)
+	}
+
+	// Test case for string with multiple valid decodings
+	if result := dynamic_programming.DecodeWays("11106"); result != 2 {
+		t.Errorf("Expected 2, got %d", result)
+	}
+}