LeetCode

Given a string S, check if the letters can be rearranged so that two characters that are adjacent to each other are not the same.

If possible, output any possible result.  If not possible, return the empty string.

Example 1:

Input: S = "aab"
Output: "aba"

Example 2:

Input: S = "aaab"
Output: ""

Note:

• S will consist of lowercase letters and have length in range [1, 500].

贪心

class Solution {
    public String reorganizeString(String S) {
        if (S == null || S.length() <= 0)
            return "";
        int[] chs = new int[26];
        for (int i=0; i<26; i++) {
            chs[i] = 0;
        }
        for (int i=0; i<S.length(); i++) {
            chs[S.charAt(i)-'a']++;
        }
        StringBuilder ret = new StringBuilder();
        char curChar = findMaxChar(chs, -1);
        while (curChar != '#' && curChar != '$') {
            ret.append(curChar);
            curChar = findMaxChar(chs, ret.charAt(ret.length()-1)-'a');
        }
        if (curChar == '$')
            return ret.toString();
        else
            return "";
    }
    
    private char findMaxChar(int[] chs, int target) {
        char ret = '#';
        int maxCnt = 0, cnt=0;
        for (int i=0; i<26; i++) {
            if (chs[i] == 0)
                cnt ++;
            if (maxCnt < chs[i] && i!=target) {
                maxCnt = chs[i];
                ret = (char)(i+'a');
            }
        }
        if (cnt == 26)
            return '$';
        if (ret != '#')
            chs[ret-'a']--;
        return ret;
    }
}