[leetCode刷题笔记]2017.03.23

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164. Maximum Gap

用桶排序的方法做。注意两个具有最大间距的两个数肯定不在一个桶。

public class Solution {    public int maximumGap(int[] nums) {        if (nums == null || nums.length < 2) {            return 0;        }         int min = nums[0];        int max = nums[0];                for (int i:nums) {            min = Math.min(min, i);            max = Math.max(max, i);        }                int gap = (int)Math.ceil((double)(max - min)/(nums.length - 1));        int[] bmin = new int[nums.length - 1];        int[] bmax = new int[nums.length - 1];        Arrays.fill(bmin, Integer.MAX_VALUE);        Arrays.fill(bmax, Integer.MIN_VALUE);                        for (int i:nums) {            if (i == min || i == max) {                continue;            }            int index = (i - min) / gap;            bmin[index] = Math.min(i, bmin[index]);            bmax[index] = Math.max(i, bmax[index]);        }                int maxgap = Integer.MIN_VALUE;        int previous = min;        for (int i = 0; i < nums.length - 1; i++) {            if (bmax[i] == Integer.MIN_VALUE && bmin[i] == Integer.MAX_VALUE) {                continue;            }            maxgap = Math.max(maxgap, bmin[i] - previous);            previous = bmax[i];        }        maxgap = Math.max(maxgap, max - previous);        return maxgap;    }}

242. Valid Anagram

public class Solution {    public boolean isAnagram(String s, String t) {        if(s==null||t==null||s.length()!=t.length())            return false;        if (s.equals(t)) {            return true;        }        int[] charset = new int[26];        for (int i = 0; i < s.length(); i++) {            charset[s.charAt(i) - 'a']++;            charset[t.charAt(i) - 'a']--;        }        for (int i:charset) {            if (i != 0) {                return false;            }        }        return true;    }}

179. Largest Number

这道题主要是修改比较器，直观的表示就是比较两个数谁当另外一个前缀得到的组合数比较大。

public class Solution {    public String largestNumber(int[] nums) {        if(nums == null || nums.length == 0)    return "";        String[] arr = new String[nums.length];        for(int i = 0; i < nums.length; i++)    arr[i] = String.valueOf(nums[i]);                Arrays.sort(arr, new Comparator<String>() {            @Override            public int compare(String s1, String s2) {                String ss1 = s1 + s2;                String ss2 = s2 + s1;                return ss2.compareTo(ss1);            }        });        if(arr[0].charAt(0) == '0')            return "0";                StringBuilder sbuilder = new StringBuilder();          for(String e : arr) {              sbuilder.append(e);          }          return sbuilder.toString();     }}

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