add leetcode Permutation in String (#1207)

* add leetcode Permutation in String

* updating DIRECTORY.md

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update leetcode/src/567.c

Co-authored-by: Stepfen Shawn <m18824909883@163.com>

* Update 567.c

fix review notes

* Update 567.c

remove redundant line

---------

Co-authored-by: github-actions[bot] <github-actions@users.noreply.github.com>
Co-authored-by: Stepfen Shawn <m18824909883@163.com>

leetcode/DIRECTORY.md

@@ -91,6 +91,7 @@
 |  509 | [Fibonacci Number](https://leetcode.com/problems/fibonacci-number)                                                                                     | [C](./src/509.c)  | Easy       |
 |  520 | [Detect Capital](https://leetcode.com/problems/detect-capital)                                                                                         | [C](./src/520.c)  | Easy       |
 |  561 | [Array Partition](https://leetcode.com/problems/array-partition)                                                                                       | [C](./src/561.c)  | Easy       |
+|  567 | [Permutation in String](https://leetcode.com/problems/permutation-in-string)                                                                           | [C](./src/567.c)  | Medium     |
 |  617 | [Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees)                                                                         | [C](./src/617.c)  | Easy       |
 |  647 | [Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings)                                                                         | [C](./src/647.c)  | Medium     |
 |  669 | [Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree)                                                                   | [C](./src/669.c)  | Medium     |

leetcode/src/567.c

@@ -0,0 +1,67 @@
+const int EnglishLettersNumber = 26;
+
+void countCharsForStringSlice(int* charsCounter, char* s, int length, int sign) {
+    for (int i = 0; i < length; i++) {
+
+        charsCounter[s[i] - 'a'] += sign;
+    }
+}
+
+// Sliding window
+// Calculate number of chars in the current slide. 
+// Runtime: O(n)
+// Space: O(1) - only number of english lowercase letters.
+bool checkInclusion(char* s1, char* s2) {
+    int lengthS1 = strlen(s1);
+    int lengthS2 = strlen(s2);
+
+    if (lengthS1 > lengthS2) {
+
+        return false;
+    }
+
+    int* charsCounter = calloc(EnglishLettersNumber, sizeof(int));
+
+    // We keep counters of s1 with '-' sign. It has to be offset by s2 chars
+    countCharsForStringSlice(charsCounter, s1, lengthS1, -1);
+    countCharsForStringSlice(charsCounter, s2, lengthS1, 1);
+
+    int diffChars = 0;
+    for (int i = 0; i < EnglishLettersNumber; i++) {
+        if (charsCounter[i] != 0) {
+            diffChars++;
+        }
+    }
+
+    if (diffChars == 0) {
+        return true;
+    }
+
+    for (int i = 0; i < lengthS2 - lengthS1; i++) {
+        int charNumberLeft = s2[i] - 'a';
+        int charNumberRight = s2[i + lengthS1] - 'a'; 
+
+        charsCounter[charNumberLeft] -= 1;
+        if (charsCounter[charNumberLeft] == 0) {
+            diffChars -= 1;
+        }
+        else if (charsCounter[charNumberLeft] == -1) {
+            diffChars += 1;
+        }
+
+        charsCounter[charNumberRight] += 1;
+        if (charsCounter[charNumberRight] == 0) {
+            diffChars -= 1;
+        }
+        else if (charsCounter[charNumberRight] == 1) {
+            diffChars += 1;
+        }
+
+        if (diffChars == 0) {
+            return true;
+        }
+    }
+
+    free(charsCounter);
+    return false;
+}