Polqt

Signed-off-by: plutov <a.pliutau@gmail.com>

Author: plutov

README.md

@@ -19,7 +19,7 @@
  - [x] ([@nguyengiabk](https://github.com/nguyengiabk), [@denpeshkov](https://github.com/denpeshkov)) [mergesort](https://github.com/plutov/practice-go/tree/master/mergesort)
  - [x] ([@nguyengiabk](https://github.com/nguyengiabk)) [wordladder](https://github.com/plutov/practice-go/tree/master/wordladder)
  - [x] ([@EvenPeng](https://github.com/EvenPeng)) [sumdecimal](https://github.com/plutov/practice-go/tree/master/sumdecimal)
- - [x] ([@bediger4000](https://github.com/bediger4000)) [buildword](https://github.com/plutov/practice-go/tree/master/buildword)
+ - [x] ([@bediger4000](https://github.com/bediger4000), [Polqt](https://github.com/Polqt)) [buildword](https://github.com/plutov/practice-go/tree/master/buildword)
  - [x] ([@zerkms](https://github.com/zerkms)) [shorthash](https://github.com/plutov/practice-go/tree/master/shorthash)
  - [x] ([@zerkms](https://github.com/zerkms)) [romannumerals](https://github.com/plutov/practice-go/tree/master/romannumerals)
  - [x] ([@zerkms](https://github.com/zerkms)) [lastlettergame](https://github.com/plutov/practice-go/tree/master/lastlettergame)

buildword/buildword_dp.go

@@ -0,0 +1,38 @@
+package buildword
+
+func BuildWordDP(word string, fragments []string) int {
+	n := len(word) // Get the length of the word
+	if n == 0 {    // If the word is empty, then we can return 0
+		return 0
+	}
+
+	// I created the dp array to store the minimum number of fragments needed to build the prefix word
+	dp := make([]int, n+1)
+
+	// Initialize the dp array with a large value (n + 1) to represent infinity
+	for i := 1; i <= n; i++ {
+		dp[i] = n + 1 // Set the initial value to n + 1 (infinity)
+	}
+
+	// For the base case, we can build an empty string with 0 fragments
+	for i := 1; i <= n; i++ {
+		for _, fragment := range fragments { // Iterate through each fragment
+			fragLen := len(fragment)
+
+			if i >= fragLen { // Does the fragment fit in the current position?
+				prevIndex := i - fragLen // Calculate the previous index
+
+				if dp[prevIndex] <= n && word[prevIndex:i] == fragment { // Check if the fragment matches the substring of the word
+					if dp[prevIndex]+1 < dp[i] { // If we can build the word with fewer fragments, update dp[i]
+						dp[i] = dp[prevIndex] + 1
+					}
+				}
+			}
+		}
+	}
+
+	if dp[n] > n { // If dp[n] is still n + 1, it means we couldn't build the word with the fragments
+		return 0
+	}
+	return dp[n] // Return the minimum number of fragments needed to build the word
+}

buildword/buildword_test.go

@@ -24,10 +24,27 @@ func TestBuildWord(t *testing.T) {
 	}
 }
 
+func TestBuildWordDP(t *testing.T) {
+	for _, test := range tests {
+		actual := BuildWordDP(test.word, test.fragments)
+		if actual != test.expected {
+			t.Errorf("BuildWordDP(%s, %v) expected %d, got %d", test.word, test.fragments, test.expected, actual)
+		}
+	}
+}
+
 func BenchmarkBuildWord(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		for _, test := range tests {
 			BuildWord(test.word, test.fragments)
 		}
 	}
 }
+
+func BenchmarkBuildWordDP(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range tests {
+			BuildWordDP(test.word, test.fragments)
+		}
+	}
+}