leetcode 28

leetcode/28/28.go

@@ -0,0 +1,44 @@
+func strStr(haystack string, needle string) int {
+    l1 := len(haystack)
+    l2 := len(needle)
+    if l2 == 0 {
+        return 0
+    }
+    if l1 == 0 {
+        return -1
+    }
+
+    next := make([]int, l2)
+    next[0] = -1
+    for k := 1; k < l2; k++ {
+        t := next[k - 1]
+        for t != -1 && needle[k-1] != needle[t]  {
+            t = next[t]
+        }
+        if t != -1 && needle[k-1] == needle[t] {
+            next[k] = t + 1
+        } else {
+            next[k] = 0
+        }
+    }
+
+    // fmt.Println(next)
+
+    i := 0
+    j := 0
+    for i != l1 {
+        // fmt.Printf("judge %d %c %d %c\n", i, haystack[i], j, needle[j]);
+        for (j != -1 && haystack[i] != needle[j]) {
+            j = next[j]
+        }
+        i++
+        j++
+        if j == l2 {
+            // fmt.Printf("match at %d\n", i - l2);
+            return i - l2
+            // i--
+            // j = next[j - 1]
+        }
+    }
+    return -1
+}