If length is even no letter should have an odd frequency. If length is odd then only one character must contain an odd count. Fill with the frequency with the count of characters. Oddc -character variable that stores the character with odd frequency(can be null)Īsf - String that stores the permutation at each level. Check whether letters of string can make a palindrome or not if it cant form a palindrome return. If the frequency of one of the character is odd, then we will find the permutation of characters with frequency half of the original (for odd character, frequency will be equal to floor(freq/2)) and then append the odd character and reverse of the permutation generated.įor example - for "aabbccc" - the permutations of "abc" are -įmap - HashMap that stores the half frequency of each character. We will generate the permutations for "ab" and append reverse of the permutation generated. We will generate the permutations for half of the frequency of each character and then append the reverse of the permutation generated.įor example - for "aabb", frequency of each character is even therefore, it is possible to generate the palindromic permutations. Way to generate palindromic permutation. If the number of the characters with odd frequency is more than 1, we will print -1 else we will generate all the palindromic permutations using recursion and backtracking. We will store the frequency of each character in a hashmap. (Example - "aabbc", "a","ahbha" have palindromic permutations but "ab","aabc" does not). To make a string palindrome, we need an even number of occurrences of letters so that the string reads the same from left and right. A permutation is a rearrangement of letters.The palindrome does not need to be limited to just dictionary words. (Example - "aabb", "aabbcc" for these inputs, palindrome will exist.)Ĭase 2 - Number of characters with odd frequency is one and rest all the characters have even frequency. A palindrome is a word or phrase that is the same forwards and backwards. We can observe those cases when the palindrome will exist.Ĭase 1 - Frequency of every character is even. Largest Number Possible After At Most K Swaps Nknights Combinations - 2d As 1d - Knight Chooses Nqueens Combinations - 2d As 1d - Queen Chooses Nqueens Permutations - 2d As 1d - Queen Chooses Queens Combinations - 2d As 1d - Queen Chooses Queens Combinations - 2d As 2d - Queen Chooses Find all possible permutations in which n people can occupy r seats in a theater. Queens Permutations - 2d As 2d - Box Chooses Program to find the largest palindrome in an array FACE Prep. Queens Combinations - 2d As 2d - Box Chooses Queens Permutations - 2d As 2d - Queen Chooses
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