Merge pull request #831 from vaskoz/day411

Day411

README.md

@@ -407,4 +407,5 @@ problems from
 * [Day 407](https://github.com/vaskoz/dailycodingproblem-go/issues/823)
 * [Day 408](https://github.com/vaskoz/dailycodingproblem-go/issues/825)
 * [Day 410](https://github.com/vaskoz/dailycodingproblem-go/issues/828)
+* [Day 411](https://github.com/vaskoz/dailycodingproblem-go/issues/830)
 

day411/problem.go

@@ -0,0 +1,73 @@
+package day411
+
+// IsKPalindromeBrute answers if the input can be made into a palindrome
+// by at most k-deletions.
+// Runtime is O(2^N).
+func IsKPalindromeBrute(str string, k int) bool {
+	orig := []rune(str)
+	rev := make([]rune, len(orig))
+
+	for i := 0; i < len(orig); i++ {
+		rev[i] = orig[len(orig)-1-i]
+	}
+
+	return isKPalindromeBrute(orig, rev, len(orig), len(rev)) <= k*2
+}
+
+func isKPalindromeBrute(orig, rev []rune, oi, ri int) int {
+	switch {
+	case oi == 0:
+		return ri
+	case ri == 0:
+		return oi
+	case orig[oi-1] == rev[ri-1]:
+		return isKPalindromeBrute(orig, rev, oi-1, ri-1)
+	default:
+		return 1 +
+			min(isKPalindromeBrute(orig, rev, oi-1, ri),
+				isKPalindromeBrute(orig, rev, oi, ri-1))
+	}
+}
+
+// IsKPalindromeDP answers if the input can be made into a palindrome
+// by at most k-deletions.
+// Runtime and space are both O(N^2) where N is the length of the input.
+func IsKPalindromeDP(str string, k int) bool {
+	orig := []rune(str)
+	rev := make([]rune, len(orig))
+
+	for i := 0; i < len(orig); i++ {
+		rev[i] = orig[len(orig)-1-i]
+	}
+
+	return isKPalindromeDP(orig, rev) <= k*2
+}
+
+func isKPalindromeDP(orig, rev []rune) int {
+	dp := make([][]int, len(orig)+1)
+	for i := range dp {
+		dp[i] = make([]int, len(orig)+1)
+		for j := range dp[i] {
+			switch {
+			case i == 0:
+				dp[i][j] = j
+			case j == 0:
+				dp[i][j] = i
+			case orig[i-1] == rev[j-1]:
+				dp[i][j] = dp[i-1][j-1]
+			default:
+				dp[i][j] = 1 + min(dp[i-1][j], dp[i][j-1])
+			}
+		}
+	}
+
+	return dp[len(orig)][len(rev)]
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+
+	return b
+}

day411/problem_test.go

@@ -0,0 +1,48 @@
+package day411
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	input    string
+	k        int
+	expected bool
+}{
+	{"waterrfetawx", 2, true},
+}
+
+func TestIsKPalindromeBrute(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if result := IsKPalindromeBrute(tc.input, tc.k); result != tc.expected {
+			t.Errorf("Expected %v got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkIsKPalindromeBrute(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			IsKPalindromeBrute(tc.input, tc.k)
+		}
+	}
+}
+
+func TestIsKPalindromeDP(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if result := IsKPalindromeDP(tc.input, tc.k); result != tc.expected {
+			t.Errorf("Expected %v got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkIsKPalindromeDP(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			IsKPalindromeDP(tc.input, tc.k)
+		}
+	}
+}