Update 17. Letter Combinations of a Phone Number.js

Tahirc1 · web-flow · commit d81656ad21a1 · 2024-10-20T15:37:21.000+05:30
diff --git a/11-20/17. Letter Combinations of a Phone Number.js b/11-20/17. Letter Combinations of a Phone Number.js
@@ -1,16 +1,31 @@
 var letterCombinations = function(digits) {
+    // if digits is empty return []
     if(digits == ""){return []}
+    // we create all possible strings a digit might correspond to
+    // digit contains number 2-9 so we keep index 0 and 1 as 0
     let k = [0,0,"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"]
+    // we convert first digit to number
     let m = Number(digits[0])
+    // we split the corresponding string to alphabets
+    // and it will store all output
     let a = k[m].split("")
     let [p,n] = [[],[]]
+    // we loop over all digits from index 1 to last index
     for(let i = 1 ; i < digits.length ;i++){
+        // p will store all possible alphabets for current digit
         p = k[digits[i]].split("")
+        // n will store all the possible combinations made for that digit
         n = []
+        // all possible combinations for given digit are are p.length*a.length
         for(let j = 0 ; j < p.length*a.length ;j++){
+            // Math.floor(j/p.length) this let us stay in range of index 0-a.length-1
+            // j%p.length  this let us stay in range of index 0-p.length-1
+            // thus going over all possible combination for all given a and p indices
             n.push(a[Math.floor(j/p.length)]+p[j%p.length])
         }
+        // we update the array a will all current possiblities
         a = n
     }
+    // we return all possible combinations
     return a
-};
+};
