Sri Hari: Batch-8/Added articles/Neetcode All (#4401)

* Batch-8/Neetcode-ALL/Added-articles

* Batch-8/Neetcode-ALL/Added-articles

* Batch-8/Neetcode-ALL/Added-articles

Author: Srihari2222

articles/add-two-numbers-ii.md

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+## 1. Custom Comparator
+
+::tabs-start
+
+```python
+class Solution:
+    def customSortString(self, order: str, s: str) -> str:
+        rank = {c: i for i, c in enumerate(order)}
+        return ''.join(sorted(s, key=lambda c: rank.get(c, 26)))
+```
+
+```java
+public class Solution {
+    public String customSortString(String order, String s) {
+        int[] rank = new int[26];
+        for (int i = 0; i < order.length(); i++) {
+            rank[order.charAt(i) - 'a'] = i + 1;
+        }
+
+        Character[] arr = new Character[s.length()];
+        for (int i = 0; i < s.length(); i++) {
+            arr[i] = s.charAt(i);
+        }
+
+        Arrays.sort(arr, (a, b) -> rank[a - 'a'] - rank[b - 'a']);
+
+        StringBuilder sb = new StringBuilder();
+        for (char c : arr) {
+            sb.append(c);
+        }
+        return sb.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string customSortString(string order, string s) {
+        vector<int> rank(26, 26);
+        for (int i = 0; i < order.size(); ++i) {
+            rank[order[i] - 'a'] = i;
+        }
+
+        sort(s.begin(), s.end(), [&](char a, char b) {
+            return rank[a - 'a'] < rank[b - 'a'];
+        });
+
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} order
+     * @param {string} s
+     * @return {string}
+     */
+    customSortString(order, s) {
+        const rank = {};
+        for (let i = 0; i < order.length; i++) {
+            rank[order[i]] = i;
+        }
+
+        return [...s].sort((a, b) => {
+            const ra = rank[a] ?? 26;
+            const rb = rank[b] ?? 26;
+            return ra - rb;
+        }).join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string CustomSortString(string order, string s) {
+        Dictionary<char, int> rank = new Dictionary<char, int>();
+        for (int i = 0; i < order.Length; i++) {
+            rank[order[i]] = i;
+        }
+
+        char[] arr = s.ToCharArray();
+        Array.Sort(arr, (a, b) => {
+            int ra = rank.ContainsKey(a) ? rank[a] : 26;
+            int rb = rank.ContainsKey(b) ? rank[b] : 26;
+            return ra - rb;
+        });
+
+        return new string(arr);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def customSortString(self, order: str, s: str) -> str:
+        count = [0] * 26
+        for c in s:
+            count[ord(c) - ord('a')] += 1
+
+        res = []
+        for c in order:
+            idx = ord(c) - ord('a')
+            while count[idx]:
+                res.append(c)
+                count[idx] -= 1
+
+        for idx in range(26):
+            c = chr(ord('a') + idx)
+            while count[idx]:
+                count[idx] -= 1
+                res.append(c)
+
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String customSortString(String order, String s) {
+        int[] count = new int[26];
+        for (char c : s.toCharArray()) {
+            count[c - 'a']++;
+        }
+
+        StringBuilder res = new StringBuilder();
+        for (char c : order.toCharArray()) {
+            int idx = c - 'a';
+            while (count[idx] > 0) {
+                res.append(c);
+                count[idx]--;
+            }
+        }
+
+        for (int idx = 0; idx < 26; idx++) {
+            char c = (char) ('a' + idx);
+            while (count[idx] > 0) {
+                res.append(c);
+                count[idx]--;
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string customSortString(string order, string s) {
+        vector<int> count(26, 0);
+        for (char c : s) {
+            count[c - 'a']++;
+        }
+
+        string res;
+        for (char c : order) {
+            int idx = c - 'a';
+            while (count[idx] > 0) {
+                res += c;
+                count[idx]--;
+            }
+        }
+
+        for (int idx = 0; idx < 26; ++idx) {
+            char c = 'a' + idx;
+            while (count[idx] > 0) {
+                res += c;
+                count[idx]--;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} order
+     * @param {string} s
+     * @return {string}
+     */
+    customSortString(order, s) {
+        const count = new Array(26).fill(0);
+        for (let c of s) {
+            count[c.charCodeAt(0) - 97]++;
+        }
+
+        const res = [];
+        for (let c of order) {
+            let idx = c.charCodeAt(0) - 97;
+            while (count[idx] > 0) {
+                res.push(c);
+                count[idx]--;
+            }
+        }
+
+        for (let idx = 0; idx < 26; idx++) {
+            let c = String.fromCharCode(97 + idx);
+            while (count[idx] > 0) {
+                res.push(c);
+                count[idx]--;
+            }
+        }
+
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string CustomSortString(string order, string s) {
+        int[] count = new int[26];
+        foreach (char c in s) {
+            count[c - 'a']++;
+        }
+
+        StringBuilder res = new StringBuilder();
+        foreach (char c in order) {
+            int idx = c - 'a';
+            while (count[idx] > 0) {
+                res.Append(c);
+                count[idx]--;
+            }
+        }
+
+        for (int idx = 0; idx < 26; idx++) {
+            char c = (char)('a' + idx);
+            while (count[idx] > 0) {
+                res.Append(c);
+                count[idx]--;
+            }
+        }
+
+        return res.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$