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import java.util.*;
public class Solution {
/**
* 26：删除数组中的重复项
* @param nums
* @return
*/
public int removeDuplicates(int[] nums) {
if (nums.length < 1) {
return 0;
}
int num = 1;
int temp = nums[0];
for (int i = 1; i < nums.length; i++) {
if (nums[i] != temp) {
num++;
nums[num - 1] = nums[i];
temp = nums[i];
}
}
return num;
}
/**
* 189：旋转数组
* @param nums
* @param k
*/
public void rotate(int[] nums, int k) {
k=k%nums.length;
reverse(nums,0,nums.length-1);
reverse(nums,0,k-1);
reverse(nums,k,nums.length-1);
}
public void reverse(int[] nums,int start,int end){
while(start<end){
int temp=nums[start];
nums[start]=nums[end];
nums[end]=temp;
start++;
end--;
}
}
class ListNode{
int val;
ListNode next;
ListNode(int x){
val=x;
}
}
/**
* 21：合并两个有序链表
* @param l1
* @param l2
* @return
*/
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1==null){
return l2;
}
if(l2==null){
return l1;
}
ListNode pre=new ListNode(0);
ListNode prev=pre;
while(l1!=null && l2!=null ){
if(l1.val<=l2.val){
prev.next=l1;
l1=l1.next;
}else{
prev.next=l2;
l2=l2.next;
}
prev=prev.next;
}
prev.next=l1==null?l2:l1;
return pre.next;
}
/**
* 合并两个有序数组
* @param nums1
* @param m
* @param nums2
* @param n
*/
public void merge(int[] nums1, int m, int[] nums2, int n) {
int n1=m-1;
int n2=n-1;
int p=m+n-1;
while(n1>=0 && n2>=0){
if(nums1[n1]<=nums2[n2]){
nums1[p]=nums2[n2];
n2--;
}else{
nums1[p]=nums1[n1];
n1--;
}
p--;
}
System.arraycopy(nums2,0,nums1,0,n2+1);
}
/**
* 1:两数之和
* @param nums
* @param target
* @return
*/
public int[] twoSum(int[] nums, int target) {
int[] result=new int[2];
Map<Integer,Integer> map=new HashMap<>();
for(int i=0;i<nums.length;i++){
int temp=target-nums[i];
if(map.containsKey(temp) && i!=map.get(temp)){
result[0]=map.get(temp);
result[1]=i;
return result;
}
map.put(nums[i],i);
}
return result;
}
/**
* 移动零
* @param nums
*/
public void moveZeroes(int[] nums) {
if(nums==null){
return;
}
int n=0;
for(int i=0;i<nums.length;i++){
if(0!=nums[i]){
n++;
nums[n-1]=nums[i];
if(n-1!=i){
nums[i]=0;
}
}
}
}
/**
* 66：加一
* @param digits
* @return
*/
public int[] plusOne(int[] digits) {
for(int i=digits.length-1;i>=0;i--){
digits[i]++;
digits[i]%= 10;
if(digits[i]!=0){
return digits;
}
}
digits=new int[digits.length+1];
digits[0]=1;
return digits;
}
/**
* 42:接雨水
* @param height
* @return
*/
public int trap(int[] height) {
int sum=0;
Stack<Integer> stack=new Stack();
int cur=0;
while(cur<height.length){
while(!stack.empty() && height[cur]>height[stack.peek()]){
int h=height[stack.pop()];
if(stack.empty()){
break;
}
int distance=cur-stack.peek()-1;
int min=Math.min(height[stack.peek()],height[cur]);
sum=sum+distance*(min-h);
}
stack.push(cur);
cur++;
}
return sum;
}
}