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mJackiemJackie
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20190122
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‎TopInterview.md‎

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| 021 | [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/) | Easy | [Java](./code/lc21.java)
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| 022 | [Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) |Medium| [Java](./code/lc22.java)
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| 023 | [Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/) | Hard | [Java](./code/lc23.java)
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| 029 |
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| 033 | [Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/) |Medium| [Java](./code/lc33.java)
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| 034 | [Search for a Range](https://leetcode.com/problems/search-for-a-range/) |Medium| [Java](./code/lc34.java)
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| 035 | [Search Insert Position](https://leetcode.com/problems/search-insert-position/) |Medium| [Java](./code/lc35.java)
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| 041 |
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| 042 | [Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/) | Hard | [Java](./code/lc42.java)
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| 044 |
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| 046 | [Permutations](https://leetcode.com/problems/permutations/) |Medium| [Java](./code/lc46.java)
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| 048 | [Rotate Image](https://leetcode.com/problems/rotate-image/) |Medium| [Java](./code/lc48.java)

‎code/lc29.java‎

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package code;
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/*
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* 29. Divide Two Integers
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* 题意：不用乘法，除法，取模运算实现除法
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* 难度：Medium
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* 分类：Math, Binary Search
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* 思路：被除数减去除数，除数每次左移一位，也就是*2 来实现类似二分的思想
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* Tips：注意下用long类型，以及溢出的情况
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*/
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public class lc29 {
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public static void main(String[] args) {
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System.out.println(divide(-1010369383,-2147483648));
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}
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public static int divide(int dividend, int divisor) {
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if(divisor==0||dividend==Integer.MIN_VALUE&&divisor==-1) return Integer.MAX_VALUE; //溢出的话直接返回最小值
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int sign;
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if( (dividend>0&&divisor>0) || (dividend<0&&divisor<0) ) sign = 1;
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else sign = -1;
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long dividend2 = Math.abs((long)dividend); //注意这要强制转换成long，再取abs
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long divisor2 = Math.abs((long)divisor);
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long div = divisor2;
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long res = 0; //这里也是long
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int p = 0;
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while( !(div>dividend2 && div==divisor2) ){
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long temp = dividend2 - div;
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if(temp>=0){
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res += Math.pow(2, p);
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p++;
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div = div << 1;
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dividend2 = temp;
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}else{
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div = divisor2;
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p = 0;
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}
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}
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return (int)res*sign;
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}
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}

‎code/lc41.java‎

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package code;
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/*
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* 41. First Missing Positive
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* 题意：返回数组中最小的未出现的正整数
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* 难度：Hard
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* 分类：Array
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* 思路：未出现的正整数一定在 [1~nums.length+1] 中，理解了这一点就好做了
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* Tips：
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*/
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public class lc41 {
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public static void main(String[] args) {
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int[] nums = {1,1};
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System.out.println(firstMissingPositive(nums));
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}
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public static int firstMissingPositive(int[] nums) {
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for (int i = 0; i < nums.length ; i++) {
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if(nums[i]>0&&nums[i]<=nums.length&&nums[nums[i]-1]!=nums[i]){ //第三个判断条件判断要交换的位置上是否已经就为了，防止重复元素死循环
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int temp = nums[nums[i]-1];
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nums[nums[i]-1] = nums[i];
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nums[i] = temp;
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i--;
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}
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}
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for (int i = 0; i < nums.length ; i++) {
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if(nums[i]!=i+1)
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return i+1;
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}
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return nums.length+1;
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}
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}

‎code/lc44.java‎

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package code;
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/*
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* 44. Wildcard Matching
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* 题意：通配符匹配
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* 难度：Hard
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* 分类：String, Dynamic Programming, Backtracking, Greedy
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* 思路：二维dp，和lc10很像，比lc10要简单一些。空间还可以压缩。
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* Tips：bingo
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*/
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public class lc44 {
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public static void main(String[] args) {
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System.out.println(isMatch("cb","?b"));
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}
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public static boolean isMatch(String s, String p) {
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boolean[][] dp = new boolean[s.length()+1][p.length()+1];
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dp[0][0] = true;
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char[] s_ch = s.toCharArray();
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char[] p_ch = p.toCharArray();
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for (int i = 0; i < p.length() ; i++) {
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if(p_ch[i]=='*') dp[0][i+1]=true;
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else break;
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}
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for (int i = 1; i <= s.length() ; i++) {
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for (int j = 1; j <= p.length() ; j++) {
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if(s_ch[i-1]==p_ch[j-1] || p_ch[j-1]=='?') dp[i][j] = dp[i-1][j-1];
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if(p_ch[j-1]=='*') dp[i][j] = dp[i-1][j-1] || dp[i-1][j] || dp[i][j-1];
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//dp[i-1][j-1] *任意第一个字符
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//dp[i-1][j] *匹配后续任意
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//dp[i][j-1] *匹配空
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}
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}
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return dp[s.length()][p.length()];
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}
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}

‎readme.md‎

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| 010 [Java](./code/lc10.java)
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| 011 [Java](./code/lc11.java)
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| 013 [Java](./code/lc13java)
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| 014 [Java](./code/lc14java)
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| 015 [Java](./code/lc15java)
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| 017 [Java](./code/lc17.java)
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| 023 [Java](./code/lc23.java)
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| 026 [Java](./code/lc26.java)
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| 028 [Java](./code/lc28.java)
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| 029 [Java](./code/lc29.java)
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| 031 [Java](./code/lc31.java)
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| 032 [Java](./code/lc32.java)
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| 033 [Java](./code/lc33.java)
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| 034 [Java](./code/lc34.java)
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| 038 [Java](./code/lc38.java)
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| 039 [Java](./code/lc39.java)
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| 041 [Java](./code/lc41.java)
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| 042 [Java](./code/lc42.java)
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| 044 [Java](./code/lc44.java)
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| 046 [Java](./code/lc46.java)
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| 048 [Java](./code/lc48.java)
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| 049 [Java](./code/lc49.java)
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| 053 [Java](./code/lc53.java)
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| 066 [Java](./code/lc66.java)
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| 070 [Java](./code/lc70.java)
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