07 - Backtracking17 - Letter Combinations Of A Phone Number â46 - Permutations & 47 - Permutations II â77-216-39-40 - Combination Sum â78 - Subsets & 90 - Subsets II â93 - Restore IP Addresses â131 - Palindrome Partitioning â491 - Non-decreasing Subsequences âåæē¯įŽæŗįčĢåēį¤ â