find-the-index-of-the-first-occurrence-in-a-string

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Algorithms

Given two strings <code>needle</code> and <code>haystack</code>, return the index of the first occurrence of <code>needle</code> in <code>haystack</code>, or <code>-1</code> if <code>needle</code> is not part of <code>haystack</code>.

&nbsp;
Example 1:

<pre>
Input: haystack = &quot;sadbutsad&quot;, needle = &quot;sad&quot;
Output: 0
Explanation: &quot;sad&quot; occurs at index 0 and 6.
The first occurrence is at index 0, so we return 0.
</pre>

Example 2:

<pre>
Input: haystack = &quot;leetcode&quot;, needle = &quot;leeto&quot;
Output: -1
Explanation: &quot;leeto&quot; did not occur in &quot;leetcode&quot;, so we return -1.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= haystack.length, needle.length &lt;= 104</code></li>
	<li><code>haystack</code> and <code>needle</code> consist of only lowercase English characters.</li>
</ul>

strStr

Find the Index of the First Occurrence in a String

Shortest Palindrome

shortest-palindrome

最短回文串

Repeated Substring Pattern

repeated-substring-pattern

重复的子字符串

Two Pointers

String

String Matching

&#32473;&#20320;&#20004;&#20010;&#23383;&#31526;&#20018;&nbsp;<code>haystack</code> &#21644; <code>needle</code> &#65292;&#35831;&#20320;&#22312; <code>haystack</code> &#23383;&#31526;&#20018;&#20013;&#25214;&#20986; <code>needle</code> &#23383;&#31526;&#20018;&#30340;&#31532;&#19968;&#20010;&#21305;&#37197;&#39033;&#30340;&#19979;&#26631;&#65288;&#19979;&#26631;&#20174; 0 &#24320;&#22987;&#65289;&#12290;&#22914;&#26524;&nbsp;<code>needle</code> &#19981;&#26159; <code>haystack</code> &#30340;&#19968;&#37096;&#20998;&#65292;&#21017;&#36820;&#22238;&nbsp; <code>-1</code> &#12290;

&nbsp;

&#31034;&#20363; 1&#65306;

<pre>
&#36755;&#20837;&#65306;haystack = "sadbutsad", needle = "sad"
&#36755;&#20986;&#65306;0
&#35299;&#37322;&#65306;"sad" &#22312;&#19979;&#26631; 0 &#21644; 6 &#22788;&#21305;&#37197;&#12290;
&#31532;&#19968;&#20010;&#21305;&#37197;&#39033;&#30340;&#19979;&#26631;&#26159; 0 &#65292;&#25152;&#20197;&#36820;&#22238; 0 &#12290;
</pre>

&#31034;&#20363; 2&#65306;

<pre>
&#36755;&#20837;&#65306;haystack = "leetcode", needle = "leeto"
&#36755;&#20986;&#65306;-1
&#35299;&#37322;&#65306;"leeto" &#27809;&#26377;&#22312; "leetcode" &#20013;&#20986;&#29616;&#65292;&#25152;&#20197;&#36820;&#22238; -1 &#12290;
</pre>

&nbsp;

&#25552;&#31034;&#65306;

<ul>
	<li><code>1 &lt;= haystack.length, needle.length &lt;= 104</code></li>
	<li><code>haystack</code> &#21644; <code>needle</code> &#20165;&#30001;&#23567;&#20889;&#33521;&#25991;&#23383;&#31526;&#32452;&#25104;</li>
</ul>

&#25214;&#20986;&#23383;&#31526;&#20018;&#20013;&#31532;&#19968;&#20010;&#21305;&#37197;&#39033;&#30340;&#19979;&#26631;

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