day 5: trying to rizz up gophy mol again

integer_to_roman.go

@@ -61,3 +61,6 @@ func intToRomanOne(num int) string {
 	// then a single allocation is made of the exact size needed for the result.
 	return r3[num%1e4/1e3] + r2[num%1e3/1e2] + r1[num%100/10] + r0[num%10]
 }
+
+
+

longest_palindrome_in_a_string.go

@@ -0,0 +1,26 @@
+package gopherriz
+
+func longestPalindromeAlternative(s string) string {
+	if len(s) < 2 {
+		return s
+	}
+
+	start, maxLength := 0, 1
+	expand := func(l, i int) {
+		for l >= 0 && i < len(s) && s[l] == s[i] {
+			if i-l+1 > maxLength {
+				start = l
+				maxLength = i - l + 1
+			}
+			l = l - 1
+			i = i + 1
+		}
+	}
+
+	for i, _ := range s {
+		expand(i, i)
+		expand(i, i+1)
+	}
+
+	return s[start : start+maxLength]
+}

manachers_algorith_longest_palindrom.go

@@ -0,0 +1,47 @@
+package gopherriz
+
+func longestPalindrome(s string) string {
+	transformed := "#"
+	for _, letter := range s {
+		transformed += string(letter) + "#"
+	}
+
+	n := len(transformed)
+	p := make([]int, n)
+	c, r := 0, 0
+	mirror := 0
+	for i := 0; i < n; i++ {
+		mirror = c*2 - i
+		if i < r {
+			p[i] = min(r-i, p[mirror])
+		}
+
+		for i+p[i]+1 < n && i-p[i]-1 >= 0 && transformed[i+p[i]+1] == transformed[i-p[i]-1] {
+			p[i] += 1
+		}
+
+		if i+p[i] > r {
+			c = i
+			r = c + p[c]
+		}
+	}
+
+	maxLength, centre := 0, 0
+	for i, v := range p {
+		if v > maxLength {
+			maxLength = v
+			centre = i
+		}
+	}
+
+	start := (centre - maxLength) / 2
+	return s[start : start+maxLength]
+
+}
+
+func min(a int, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}