28. Find the Index of the First Occurrence in a String

```Solution.c int strStr(char * haystack, char * needle){ int n = strlen(haystack), m = strlen(needle); if (m == 0) return 0; int lps[m]; lps[0] = 0; for (int i = 1, len = 0; i < m; ) { if (needle[i] == needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (int i = 0, j = 0; i < n; ) { if (haystack[i] == needle[j]) { i++; j++; if (j == m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } ``` ```Solution.cpp class Solution { public: int strStr(string haystack, string needle) { int n = haystack.size(), m = needle.size(); if (m == 0) return 0; vector<int> lps(m, 0); for (int i = 1, len = 0; i < m; ) { if (needle[i] == needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (int i = 0, j = 0; i < n; ) { if (haystack[i] == needle[j]) { i++; j++; if (j == m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } }; ``` ```Solution.cs public class Solution { public int StrStr(string haystack, string needle) { int n = haystack.Length, m = needle.Length; if (m == 0) return 0; int[] lps = new int[m]; for (int i = 1, len = 0; i < m; ) { if (needle[i] == needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (int i = 0, j = 0; i < n; ) { if (haystack[i] == needle[j]) { i++; j++; if (j == m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } } ``` ```Solution.dart class Solution { int strStr(String haystack, String needle) { int n = haystack.length, m = needle.length; if (m == 0) return 0; List<int> lps = List.filled(m, 0); for (int i = 1, len = 0; i < m;) { if (needle[i] == needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (int i = 0, j = 0; i < n;) { if (haystack[i] == needle[j]) { i++; j++; if (j == m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } } ``` ```Solution.erl -spec str_str(Haystack :: unicode:unicode_binary(), Needle :: unicode:unicode_binary()) -> integer(). str_str(Haystack, Needle) -> case Needle of <<>> -> 0; _ -> case binary:match(Haystack, Needle) of nomatch -> -1; {Pos, _Len} -> Pos end end. ``` ```Solution.ex defmodule Solution do @SPEC str_str(haystack :: String.t(), needle :: String.t()) :: integer def str_str(haystack, needle) do cond do needle == "" -> 0 true -> case :binary.match(haystack, needle) do :nomatch -> -1 {pos, _len} -> pos end end end end ``` ```Solution.go func strStr(haystack string, needle string) int { n, m := len(haystack), len(needle) if m == 0 { return 0 } lps := make([]int, m) for i, length := 1, 0; i < m; { if needle[i] == needle[length] { length++ lps[i] = length i++ } else if length > 0 { length = lps[length-1] } else { lps[i] = 0 i++ } } for i, j := 0, 0; i < n; { if haystack[i] == needle[j] { i++; j++ if j == m { return i - m } } else if j > 0 { j = lps[j-1] } else { i++ } } return -1 } ``` ```Solution.java class Solution { public int strStr(String haystack, String needle) { int n = haystack.length(), m = needle.length(); if (m == 0) return 0; int[] lps = new int[m]; for (int i = 1, len = 0; i < m; ) { if (needle.charAt(i) == needle.charAt(len)) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (int i = 0, j = 0; i < n; ) { if (haystack.charAt(i) == needle.charAt(j)) { i++; j++; if (j == m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } } ``` ```Solution.js /** * @param {string} haystack * @param {string} needle * @return {number} */ var strStr = function(haystack, needle) { const n = haystack.length, m = needle.length; if (m === 0) return 0; const lps = new Array(m).fill(0); for (let i = 1, len = 0; i < m;) { if (needle[i] === needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (let i = 0, j = 0; i < n;) { if (haystack[i] === needle[j]) { i++; j++; if (j === m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; }; ``` ```Solution.kt class Solution { fun strStr(haystack: String, needle: String): Int { val n = haystack.length val m = needle.length if (m == 0) return 0 val lps = IntArray(m) var len = 0 var i = 1 while (i < m) { if (needle[i] == needle[len]) { len++ lps[i] = len i++ } else if (len > 0) { len = lps[len - 1] } else { lps[i] = 0 i++ } } i = 0; var j = 0 while (i < n) { if (haystack[i] == needle[j]) { i++; j++ if (j == m) return i - m } else if (j > 0) { j = lps[j - 1] } else { i++ } } return -1 } } ``` ```Solution.php class Solution { /** * @param String $haystack * @param String $needle * @return Integer */ function strStr($haystack, $needle) { $n = strlen($haystack); $m = strlen($needle); if ($m == 0) return 0; $lps = array_fill(0, $m, 0); for ($i = 1, $len = 0; $i < $m; ) { if ($needle[$i] == $needle[$len]) { $lps[$i++] = ++$len; } elseif ($len > 0) { $len = $lps[$len - 1]; } else { $lps[$i++] = 0; } } for ($i = 0, $j = 0; $i < $n; ) { if ($haystack[$i] == $needle[$j]) { $i++; $j++; if ($j == $m) return $i - $m; } elseif ($j > 0) { $j = $lps[$j - 1]; } else { $i++; } } return -1; } } ``` ```Solution.py class Solution: def strStr(self, haystack: str, needle: str) -> int: n, m = len(haystack), len(needle) if m == 0: return 0 lps = [0] * m length = 0 i = 1 while i < m: if needle[i] == needle[length]: length += 1 lps[i] = length i += 1 elif length > 0: length = lps[length - 1] else: lps[i] = 0 i += 1 i = j = 0 while i < n: if haystack[i] == needle[j]: i += 1 j += 1 if j == m: return i - m elif j > 0: j = lps[j - 1] else: i += 1 return -1 ``` ```Solution.rb # @param {String} haystack # @param {String} needle # @return {Integer} def str_str(haystack, needle) n, m = haystack.length, needle.length return 0 if m == 0 lps = Array.new(m, 0) len = 0; i = 1 while i < m if needle[i] == needle[len] len += 1 lps[i] = len i += 1 elsif len > 0 len = lps[len - 1] else lps[i] = 0 i += 1 end end i = j = 0 while i < n if haystack[i] == needle[j] i += 1; j += 1 return i - m if j == m elsif j > 0 j = lps[j - 1] else i += 1 end end -1 end ``` ```Solution.rkt (define/contract (str-str haystack needle) (-> string? string? exact-integer?) (let* ((n (string-length haystack)) (m (string-length needle))) (cond [(= m 0) 0] [else (define lps (make-vector m 0)) (let loop ((i 1) (len 0)) (when (< i m) (cond [(char=? (string-ref needle i) (string-ref needle len)) (set! len (add1 len)) (vector-set! lps i len) (loop (add1 i) len)] [(> len 0) (loop i (vector-ref lps (sub1 len)))] [else (vector-set! lps i 0) (loop (add1 i) len)]))) (let search ((i 0) (j 0)) (cond [(= i n) -1] [(char=? (string-ref haystack i) (string-ref needle j)) (if (= (add1 j) m) (- (add1 i) m) (search (add1 i) (add1 j)))] [(> j 0) (search i (vector-ref lps (sub1 j)))] [else (search (add1 i) j)]))]))) ``` ```Solution.rs impl Solution { pub fn str_str(haystack: String, needle: String) -> i32 { let n = haystack.len(); let m = needle.len(); if m == 0 { return 0; } let h: Vec<char> = haystack.chars().collect(); let nd: Vec<char> = needle.chars().collect(); let mut lps = vec![0; m]; let (mut len, mut i) = (0, 1); while i < m { if nd[i] == nd[len] { len += 1; lps[i] = len; i += 1; } else if len > 0 { len = lps[len - 1]; } else { lps[i] = 0; i += 1; } } let (mut j, mut idx) = (0, 0); while idx < n { if h[idx] == nd[j] { idx += 1; j += 1; if j == m { return (idx - m) as i32; } } else if j > 0 { j = lps[j - 1]; } else { idx += 1; } } -1 } } ``` ```Solution.scala object Solution { def strStr(haystack: String, needle: String): Int = { val n = haystack.length val m = needle.length if (m == 0) return 0 val lps = Array.fill(m)(0) var len = 0 var i = 1 while (i < m) { if (needle(i) == needle(len)) { len += 1 lps(i) = len i += 1 } else if (len > 0) { len = lps(len - 1) } else { lps(i) = 0 i += 1 } } i = 0; var j = 0 while (i < n) { if (haystack(i) == needle(j)) { i += 1; j += 1 if (j == m) return i - m } else if (j > 0) { j = lps(j - 1) } else { i += 1 } } -1 } } ``` ```Solution.swift class Solution { func strStr(_ haystack: String, _ needle: String) -> Int { let n = haystack.count, m = needle.count if m == 0 { return 0 } let h = Array(haystack), nd = Array(needle) var lps = [Int](repeating: 0, count: m) var len = 0, i = 1 while i < m { if nd[i] == nd[len] { len += 1 lps[i] = len i += 1 } else if len > 0 { len = lps[len - 1] } else { lps[i] = 0 i += 1 } } i = 0; var j = 0 while i < n { if h[i] == nd[j] { i += 1; j += 1 if j == m { return i - m } } else if j > 0 { j = lps[j - 1] } else { i += 1 } } return -1 } } ``` ```Solution.ts function strStr(haystack: string, needle: string): number { const n = haystack.length, m = needle.length; if (m === 0) return 0; const lps: number[] = new Array(m).fill(0); for (let i = 1, len = 0; i < m;) { if (needle[i] === needle[len]) { lps[i++] = ++len; } else if (len > 0) { len = lps[len - 1]; } else { lps[i++] = 0; } } for (let i = 0, j = 0; i < n;) { if (haystack[i] === needle[j]) { i++; j++; if (j === m) return i - m; } else if (j > 0) { j = lps[j - 1]; } else { i++; } } return -1; } ```

Author: nendroids

sol/solution/0001-0100/0028/README.md

@@ -0,0 +1,22 @@
+# [**28. Find the Index of the First Occurrence in a String**](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/description/)
+
+Given two strings `needle` and `haystack`, return the index of the first occurrence of `needle` in `haystack`, or `-1` if `needle` is not part of `haystack`.
+
+#### **Example 1:**
+```MD
+Input: haystack = "sadbutsad", needle = "sad"
+Output: 0
+Explanation: "sad" occurs at index 0 and 6.
+The first occurrence is at index 0, so we return 0.
+```
+
+#### **Example 2:**
+```md
+Input: haystack = "leetcode", needle = "leeto"
+Output: -1
+Explanation: "leeto" did not occur in "leetcode", so we return -1.
+```
+
+#### **Constraints:**
+> - `1 <= haystack.length, needle.length <= 104`
+> - `haystack` and `needle` consist of only lowercase English characters.

sol/solution/0001-0100/0028/Solution.c

@@ -0,0 +1,26 @@
+int strStr(char * haystack, char * needle){
+ int n = strlen(haystack), m = strlen(needle);
+ if (m == 0) return 0;
+ int lps[m];
+ lps[0] = 0;
+ for (int i = 1, len = 0; i < m; ) {
+ if (needle[i] == needle[len]) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (int i = 0, j = 0; i < n; ) {
+ if (haystack[i] == needle[j]) {
+ i++; j++;
+ if (j == m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+}

sol/solution/0001-0100/0028/Solution.cpp

@@ -0,0 +1,28 @@
+class Solution {
+public:
+ int strStr(string haystack, string needle) {
+ int n = haystack.size(), m = needle.size();
+ if (m == 0) return 0;
+ vector<int> lps(m, 0);
+ for (int i = 1, len = 0; i < m; ) {
+ if (needle[i] == needle[len]) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (int i = 0, j = 0; i < n; ) {
+ if (haystack[i] == needle[j]) {
+ i++; j++;
+ if (j == m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+ }
+};

sol/solution/0001-0100/0028/Solution.cs

@@ -0,0 +1,27 @@
+public class Solution {
+ public int StrStr(string haystack, string needle) {
+ int n = haystack.Length, m = needle.Length;
+ if (m == 0) return 0;
+ int[] lps = new int[m];
+ for (int i = 1, len = 0; i < m; ) {
+ if (needle[i] == needle[len]) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (int i = 0, j = 0; i < n; ) {
+ if (haystack[i] == needle[j]) {
+ i++; j++;
+ if (j == m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+ }
+}

sol/solution/0001-0100/0028/Solution.dart

@@ -0,0 +1,27 @@
+class Solution {
+ int strStr(String haystack, String needle) {
+ int n = haystack.length, m = needle.length;
+ if (m == 0) return 0;
+ List<int> lps = List.filled(m, 0);
+ for (int i = 1, len = 0; i < m;) {
+ if (needle[i] == needle[len]) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (int i = 0, j = 0; i < n;) {
+ if (haystack[i] == needle[j]) {
+ i++; j++;
+ if (j == m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+ }
+}

sol/solution/0001-0100/0028/Solution.erl

@@ -0,0 +1,11 @@
+-spec str_str(Haystack :: unicode:unicode_binary(),
+ Needle :: unicode:unicode_binary()) -> integer().
+str_str(Haystack, Needle) ->
+ case Needle of
+ <<>> -> 0;
+ _ ->
+ case binary:match(Haystack, Needle) of
+ nomatch -> -1;
+ {Pos, _Len} -> Pos
+ end
+ end.

sol/solution/0001-0100/0028/Solution.ex

@@ -0,0 +1,14 @@
+defmodule Solution do
+ @spec str_str(haystack :: String.t(), needle :: String.t()) :: integer
+ def str_str(haystack, needle) do
+ cond do
+ needle == "" ->
+ 0
+ true ->
+ case :binary.match(haystack, needle) do
+ :nomatch -> -1
+ {pos, _len} -> pos
+ end
+ end
+ end
+end

sol/solution/0001-0100/0028/Solution.go

@@ -0,0 +1,32 @@
+func strStr(haystack string, needle string) int {
+ n, m := len(haystack), len(needle)
+ if m == 0 {
+ return 0
+ }
+ lps := make([]int, m)
+ for i, length := 1, 0; i < m; {
+ if needle[i] == needle[length] {
+ length++
+ lps[i] = length
+ i++
+ } else if length > 0 {
+ length = lps[length-1]
+ } else {
+ lps[i] = 0
+ i++
+ }
+ }
+ for i, j := 0, 0; i < n; {
+ if haystack[i] == needle[j] {
+ i++; j++
+ if j == m {
+ return i - m
+ }
+ } else if j > 0 {
+ j = lps[j-1]
+ } else {
+ i++
+ }
+ }
+ return -1
+}

sol/solution/0001-0100/0028/Solution.java

@@ -0,0 +1,27 @@
+class Solution {
+ public int strStr(String haystack, String needle) {
+ int n = haystack.length(), m = needle.length();
+ if (m == 0) return 0;
+ int[] lps = new int[m];
+ for (int i = 1, len = 0; i < m; ) {
+ if (needle.charAt(i) == needle.charAt(len)) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (int i = 0, j = 0; i < n; ) {
+ if (haystack.charAt(i) == needle.charAt(j)) {
+ i++; j++;
+ if (j == m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+ }
+}

sol/solution/0001-0100/0028/Solution.js

@@ -0,0 +1,30 @@
+/**
+ * @param {string} haystack
+ * @param {string} needle
+ * @return {number}
+ */
+var strStr = function(haystack, needle) {
+ const n = haystack.length, m = needle.length;
+ if (m === 0) return 0;
+ const lps = new Array(m).fill(0);
+ for (let i = 1, len = 0; i < m;) {
+ if (needle[i] === needle[len]) {
+ lps[i++] = ++len;
+ } else if (len > 0) {
+ len = lps[len - 1];
+ } else {
+ lps[i++] = 0;
+ }
+ }
+ for (let i = 0, j = 0; i < n;) {
+ if (haystack[i] === needle[j]) {
+ i++; j++;
+ if (j === m) return i - m;
+ } else if (j > 0) {
+ j = lps[j - 1];
+ } else {
+ i++;
+ }
+ }
+ return -1;
+};