leetcode面试经典150题- 28. 找出字符串中第一个匹配项的下标

https://leetcode.cn/problems/find-the-index-of-the-first-occurrence-in-a-string/description/?envType=study-plan-v2&envId=top-interview-150

 

package leetcode150

import "testing"

func TestStrStr(t *testing.T) {
    haystack := "sadbutsad"
    needle := "sad"
    res := strStr(haystack, needle)
    println(res)
}

func strStr(haystack string, needle string) int {
    next := make([]int, len(needle))
    next[0] = 0
    i, j := 1, 0
    for ; i < len(needle); i++ {
        for j > 0 && needle[i] != needle[j] {
            j = next[j-1]
        }
        if needle[i] == needle[j] {
            j++
        }
        next[i] = j
    }

    //for _, o := range next {
    //    print(o)
    //    print(" ")
    //}
    //println()
    for i, j = 0, 0; i < len(haystack); i++ {
        for j > 0 && haystack[i] != needle[j] {
            j = next[j-1]
        }

        if haystack[i] == needle[j] {
            j++
        }

        if j == len(needle) {
            return i - j + 1
        }
    }

    return -1
}