Runtime: 29 ms (Top 84.38%) | Memory: 106.10 MB (Top 54.69%)

Author: AnasImloul

scripts/algorithms/C/Can Make Palindrome from Substring/Can Make Palindrome from Substring.java

@@ -1,12 +1,23 @@
+// Runtime: 29 ms (Top 84.38%) | Memory: 106.10 MB (Top 54.69%)
+
 class Solution 
-{
-    public List<Boolean> canMakePaliQueries(String s, int[][] queries) 
+{ public List<Boolean> canMakePaliQueries(String s, int[][] queries) 
     {
         List<Boolean> list = new ArrayList<>();
 
         int n = s.length();
+        // prefix map to count number of time each letters have occured to access in queries in O(1)
+       //s=  a b c d a
+        // a 1 1 1 1 2
+        // b 0 1 1 1 1
+        // c 0 0 1 1 1
+        // d 0 0 0 1 1
+        // e
+        // f
+        // .
+        // .
+        // .
         int[][] map = new int[n+1][26];
-        
         for(int i=0;i<s.length();i++)
         {
             for(int j=0;j<26;j++)
@@ -23,9 +34,9 @@ public List<Boolean> canMakePaliQueries(String s, int[][] queries)
             int count = 0;
 
             for(int i=0;i<26;i++)
-                count += (map[r+1][i] - map[l][i]) % 2;
+                count += (map[r+1][i] - map[l][i]) % 2;// count total characters that have odd count, so that we can replace the half of them with their pair.
 
-            list.add(count/2 <= k);
+            list.add(count/2 <= k);// if we can replace half of them with their pair
         }
 
         return list;