leetcode 340. Longest Substring with At Most K Distinct Characters

leetcode 340. Longest Substring with At Most K Distinct Characters

下面的实现是很直观的，记下当前所包含的字符数，采用双指针进行移动

public class Solution {public static void main(String[] args){Solution s = new Solution();s.lengthOfLongestSubstringKDistinct("abacccc", 2);}    public int lengthOfLongestSubstringKDistinct(String s, int k) {        int size = s.length();        if(size<=k) return size;        if(k==0)  return 0;    char[] chars = s.toCharArray();        int i=0,j=0;        int max = 0;//        HashSet<Character> bag = new HashSet<Character>();        HashMap<Character, Integer> bag = new HashMap<Character, Integer>(); //        bag.add(chars[0]);        bag.put(chars[0], 1);        while(i<size&&j<size){//        System.out.println(bag.size());        if(bag.size()<=k){        max = max > (j-i+1) ? max :(j-i+1);//        System.out.println(max);        j++;        if(j<size) {//        bag.add(chars[j]);        if(bag.containsKey(chars[j]))         bag.put(chars[j], bag.get(chars[j])+1);        else        bag.put(chars[j], 1);        }        if(j==size) break;        }else{        i++;        if(i<size) {        // System.out.println(i);        // System.out.println(j);        bag.put(chars[i-1], bag.get(chars[i-1])-1);        if(bag.get(chars[i-1])==0)        bag.remove(chars[i-1]);        }        }        }        return max;    }}

而下面这种解法，在i 自增的时候，不再是一步一步增，直接跳转到所有元素最右出现的位置的最小位置（有点绕，但是对的）

class Solution(object):    def lengthOfLongestSubstringKDistinct(self, s, k):        """        :type s: str        :type k: int        :rtype: int        """        d = {}        low, ret = 0, 0        for i, c in enumerate(s):            d[c] = i            if len(d) > k:                low = min(d.values())                print(low)                del d[s[low]]                print(d)                low += 1            ret = max(i - low + 1, ret)        return ret        

java  版本

import java.util.HashMap;import java.util.HashSet;import java.util.Map;public class Solution {public static void main(String[] args){Solution s = new Solution();s.lengthOfLongestSubstringKDistinct("abacccc", 2);}    public int lengthOfLongestSubstringKDistinct(String s, int k) {        int size = s.length();        if(size<=k) return size;        if(k==0)  return 0;    char[] chars = s.toCharArray();        int i=0,low=0;        int max = 0;//        HashSet<Character> bag = new HashSet<Character>();        HashMap<Character, Integer> bag = new HashMap<Character, Integer>(); //        bag.add(chars[0]);        while(i<size){        bag.put(chars[i], i);        if(bag.size()>k){        low = findmin(bag);        bag.remove(chars[low]);        low = low + 1;        }        max = max>(i-low+1)?max:(i-low+1);            i+=1;        }        return max;    }        public int findmin(HashMap<Character, Integer> bag){    int min = Integer.MAX_VALUE;    for(Map.Entry<Character, Integer> entry: bag.entrySet()){    if(entry.getValue()<min){    min = entry.getValue();    }    }    return min;    }    }