zigzag debug ing

go/cmd/demo.go

@@ -23,6 +23,10 @@ var demoCmd = &cobra.Command{
 // utf8.RuneCountInString("Hi")
 
 func demoMain() {
+	// demo.Convert("A", 1)
+	demo.Convert("ABC", 2)
 	r := demo.Convert("PAYPALISHIRING", 3)
 	fmt.Println(r == "PAHNAPLSIIGYIR", r)
+	fmt.Println(r)
+	fmt.Println("PAHNAPLSIIGYIR")
 }

go/demo/leetcode.go

@@ -1,6 +1,7 @@
 package demo
 
 import (
+	"fmt"
 	"math/bits"
 	"unicode/utf8"
 
@@ -265,8 +266,55 @@ func LongestPalindrome(s string) string {
 func Convert(s string, numRows int) string {
 	r := []rune(s)
 	l := len(r)
-	for i := 0; i < l; i++ {
+	t := make([]rune, l)
 
+	start := numRows + numRows - 2
+	offset := make([]int, start)
+
+	for i, c := 0, 0; i < start; i++ {
+		if c == 0 {
+			c = start
+		}
+		offset[i] = c
+		c -= 2
+	}
+	fmt.Println(offset)
+
+	ti := 0
+	for row := 0; row < numRows; row++ {
+		o1, o2 := start-(row*2), row*2
+
+		fmt.Println("row ", row, o1, o2)
+		if row == 0 || row == numRows-1 {
+			o := Max(o1, o2)
+			si := row
+			for i := 0; ; i++ {
+				si += i * o
+				if si >= l {
+					break
+				}
+				t[ti] = r[si]
+				ti++
+			}
+		} else {
+			si := row
+			for i := 0; ; i += 1 {
+				si += o1
+				if si >= l {
+					break
+				}
+				t[ti] = r[si]
+				ti++
+				si += o2
+				if si >= l {
+					break
+				}
+				t[ti] = r[si]
+				ti++
+			}
+		}
 	}
-	return string(r)
+	fmt.Println(ti, ti == l, string(t))
+
+	return string(t)
 }