剑指offer 数组专题 刷题记录（3）

public class Solution {
    public int InversePairs(int [] array) {
        if(array.length==0||array==null){
            return 0;
        }
        int[] copyArray=new int[array.length];
        int count=InversePairs(array,copyArray,0,array.length-1);
        return count;
    }
    public int InversePairs(int[] array,int[] copyArray,int low,int high){
        if(low==high)
            return 0;
        int mid=low+(high-low)/2;
        int i=mid;
        int j=high;
        int localCopy=high;
        int count=0;
        int leftCount=InversePairs(array,copyArray,low,mid)%1000000007;
        int rightCount=InversePairs(array,copyArray,mid+1,high)%1000000007;
        while(i>=low&&j>mid){
            if(array[i]>array[j]){
                copyArray[localCopy--]=array[i--];
                count+=j-mid;
                if(count>1000000007){
                    count=count%1000000007;
                }
            }else{
                copyArray[localCopy--]=array[j--];
            }
        }
        while(i>=low){
            copyArray[localCopy--]=array[i--];
        }
        while(j>mid){
            copyArray[localCopy--]=array[j--];
        }
        for(int k=low;k<=high;k++){
            array[k]=copyArray[k];
        }
        return  (leftCount+rightCount+count)%1000000007;
    }
}

public class Solution {
    public int GetNumberOfK(int [] array , int k) {
        int count=0;
       for(int i=0;i<array.length;i++){
           if(array[i]==k){
               count++;
           }
       }
        return count;
    }
}

二分查找，参考剑指Offer,但是用的非递归。
public class Solution {
      public  int GetNumberOfK(int[] array,int k){
    if(array==null||array.length==0)
      return 0;
    int first=getFirstK(array,k,0,array.length-1);
    int last=getLastK(array,k,0,array.length-1);
    if(first==-1 ||last==-1){
      return 0;
    }
    else{
      return last-first+1;
    }
  }
  public  int getFirstK(int[] array,int k,int start,int end){
    while(start<=end){
      int mid=(start+end)/2;
      if(k<array[mid])
        end=mid-1;
      else if(k>array[mid])
        start=mid+1;
      else{
        if((mid>0&&array[mid-1]!=k)||mid==0)
          return mid;
        else{
          end=mid-1;
        }
      }
    }
    return -1;
  }
  public  int getLastK(int[] array,int k ,int start,int end){
    while(start<=end){
      int mid=(start+end)/2;
      if(k<array[mid])
        end=mid-1;
      else if(k>array[mid])
        start=mid+1;
      else{
        if((mid<array.length-1&&array[mid+1]!=k)||mid==array.length-1)
          return mid;
        else{
          start=mid+1;
        }
      }
    }
    return -1;
  }
}

import java.util.*;
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 array int整型一维数组 
     * @return int整型一维数组
     */
    public int[] FindNumsAppearOnce (int[] array) {
        // write code here
        Map<Integer,Integer> map=new HashMap<Integer,Integer>();
        for(int i=0;i<array.length;i++){
            if(map.containsKey(array[i])){
                map.put(array[i],map.get(array[i])+1);
            }else{
                map.put(array[i],1);
            }
        }
        int[] res=new int[2];
        int index=0;
        for(Map.Entry<Integer,Integer> entry:map.entrySet()){
            if(entry.getValue()==1){
                res[index]=entry.getKey();
                index++;
            }
        }
        return res;
    }
}