题解 | #eli和字符串#

import java.util.*;

/**
 * NC400 eli和字符串
 * @author d3y1
 */
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param str string字符串 
     * @param k int整型 
     * @return int整型
     */
    public int eliStr (String str, int k) {
        return solution(str, k);
    }

    /**
     * 双指针
     * @param str
     * @param k
     * @return
     */
    private int solution(String str, int k){
        int len = str.length();
        int[] count = new int[26];
        char chR,chL;
        int result = Integer.MAX_VALUE;
        for(int i=0,j=0; j<len; j++){
            chR = str.charAt(j);
            count[chR-'a']++;
            while(count[chR-'a'] == k){
                result = Math.min(result, j-i+1);
                chL = str.charAt(i);
                count[chL-'a']--;
                i++;
            }
        }

        if(result == Integer.MAX_VALUE){
            result = -1;
        }

        return result;
    }
}