day-18

Author: libterty

README.md

@@ -16,5 +16,6 @@
     -   Day 13: [Remove K Digits](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-thirteen/index.ts) :tongue:
     -   Day 14: [Implement Trie (Prefix Tree)](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-thirteen/index.ts) :pig_nose:
     -   Day 15: [Maximum Sum Circular Subarray](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-fifteen/index.ts) :whale:
-    -   Day 16: [Odd Even Linked List](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-sixteen/index.ts) :whale:
-    -   Day 17: [Find All Anagrams in a String Solution](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-seventeen/index.ts) :whale:
+    -   Day 16: [Odd Even Linked List](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-sixteen/index.ts) :grin:
+    -   Day 17: [Find All Anagrams in a String Solution](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-seventeen/index.ts) :hear_no_evil:
+    -   Day 18: [Permutation in String](https://github.com/libterty/leetcode-challenge/blob/master/src/may/day-eighteen/index.ts) :pig_nose:

src/may/day-eighteen/index.ts

@@ -0,0 +1,43 @@
+/**
+ * @param {string} s1
+ * @param {string} s2
+ * @return {boolean}
+ */
+
+var checkInclusion = function (s1: string, s2: string): boolean {
+    const len1: number = s1.length;
+    const len2: number = s2.length;
+
+    if (len1 > len2) return false;
+    let alphas = Array.from({ length: 26 }, (x) => 0);
+    let begin = 'a'.charCodeAt(0);
+    for (let a of s1) alphas[a.charCodeAt(0) - begin]++;
+
+    let len = s1.length;
+    let count = Array.from({ length: 26 }, (x) => 0);
+    //initialize count
+    for (let i = 0; i < len; i++) {
+        count[s2[i].charCodeAt(0) - begin]++;
+    }
+
+    //sliding window
+    for (let i = len; i <= s2.length; i++) {
+        let fit = true;
+        for (let i = 0; i < 26; i++) {
+            if (count[i] !== alphas[i]) {
+                fit = false;
+                break;
+            }
+        }
+        if (fit) return true;
+        if (i === s2.length) return false;
+        //update count
+        count[s2[i - len].charCodeAt(0) - begin]--;
+        count[s2[i].charCodeAt(0) - begin]++;
+    }
+};
+
+const cd = checkInclusion('ab', 'eidbaooo');
+const de = checkInclusion('abc', 'ccccbbbbaaaa');
+console.log('cd', cd);
+console.log('de', de);