add: 在字符串中查找给定的子字符串出现的第一个位置

README.md

@@ -68,7 +68,7 @@
 5. [电话号码中的字符组合](https://github.com/dengshasha/algorithm-study/blob/master/string/letterCombOfPhoneNum.js) || [leetcode地址](https://leetcode.com/problems/letter-combinations-of-a-phone-number/submissions/)
 6. [爬楼梯](https://github.com/dengshasha/algorithm-study/blob/master/string/climbStairs.js) || [leetcode地址](https://leetcode.com/problems/climbing-stairs/)
 7. [在字符串中查找满足条件的最短子串](https://github.com/dengshasha/algorithm-study/blob/master/string/minWindowSubstr.js) || [leetcode地址](https://leetcode.com/problems/minimum-window-substring/)
-
+8. [在字符串中查找给定的子字符串出现的第一个位置](https://github.com/dengshasha/algorithm-study/blob/master/string/findFirstPosOfStr.js) || [leetcode地址](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/)
 
 ### 数组
 1. [数组各项，除该项外累乘的结果](https://github.com/dengshasha/algorithm-study/blob/master/array/productArrayExceptSelf.js) || [leetcode地址](https://leetcode.com/problems/product-of-array-except-self/submissions/)

string/findFirstPosOfStr.js

@@ -0,0 +1,38 @@
+/**
+ * Created by dengxuelian on 2022/11/4
+ */
+/**
+ * @param {string} haystack
+ * @param {string} needle
+ * @return {number}
+ */
+// 解法1
+var strStr = function(haystack, needle) {
+    let h_size = haystack.length, n_size = needle.length;
+
+    for(let i = 0; i <= h_size - n_size; i++) {
+        if(haystack[i] !== needle[0]) continue;
+        if(findSubStr(i, needle)) {
+            return i
+        }
+    }
+
+    function findSubStr(index, str) {
+        if(str === '') return true;
+        if(index >= h_size || haystack[index] !== str[0]) return false;
+        return findSubStr(index+1, str.slice(1))
+    }
+    return -1
+};
+
+//解法2
+var strStr_1 = function(haystack, needle) {
+    let h_size = haystack.length, n_size = needle.length;
+    let start = 0, end = n_size;
+    while(end <= h_size) {
+        if(haystack.slice(start, end) === needle) return start;
+        start++;
+        end++;
+    }
+    return -1
+}