[LeetCode] 28. Implement strStr() java

2019-11-06 06:19:25

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/**28. Implement strStr() * @param haystack * @param needle * @returnint needle是不是haystack的子串，是的话就返回这个子串 */ public int strStr(String haystack, String needle) { if (haystack == null || needle == null) return -1; if (haystack.length() < needle.length()) return -1; int hlen = haystack.length(); int nlen = needle.length(); for (int i=0; i<=hlen-nlen; i++) { String str = haystack.substring(i, i+nlen); if (str.equals(needle)) { return i; } } return -1; }

每次截取等长字符串，进行比较

数据结构中关于子串的KMP算法

public int strStr1(String haystack, String needle) { for (int i = 0;; i++) { for (int j = 0;; j++) { if (j == needle.length()) return i; if (i + j == haystack.length()) return -1; if (needle.charAt(j) != haystack.charAt(i + j)) break; } } }

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