• 【排序】


    1. 归并排序<可求逆序对>
       1 #include<iostream>
       2 #include<cstdio>
       3 using namespace std;
       4 long long n, a[1000100], c[1000100];
       5 long long ans=0;
       6 void merge(int l, int r)
       7 {
       8     if(l==r)    return ;
       9     int mid = (l + r) / 2;
      10     merge(l,mid);
      11     merge(mid+1,r);
      12     int i = l, j = mid + 1, k = 1;
      13     while (i <= mid && j <= r)
      14     {
      15         if (a[i] <= a[j])
      16             c[k++] = a[i++];
      17         else
      18         {    c[k++] = a[j++];
      19             ans+=mid-i+1;
      20         }
      21     }
      22     while (i <= mid)    c[k++] = a[i++];
      23     while (j <= r)    c[k++] = a[j++];    
      24     for (i = l, k = 1; i <= r; i++)
      25         a[i] = c[k++];
      26     
      27 }
      28 int main()
      29 {
      30     cin >> n;
      31     for (int i = 1; i <= n; i++)
      32         cin >> a[i];
      33     merge(1,n);
      34     cout<<ans<<endl;
      35     return 0;
      36 }
      哈哈哈你来打我啊
    2. 快速幂
       1 #include<iostream>
       2 using namespace std;
       3 //求b^P
       4 int b,p;
       5 void work()
       6 {
       7     long long ans=1;
       8     int t=p,s=b;
       9     while(t!=0)
      10     {
      11         if(t%2==1)  ans=ans*s;
      12         t/=2;
      13         s=s*s;
      14     }
      15 }
      16 int main()
      17 {
      18     cin>>b>>p;
      19     work();
      20     cout<<ans<<endl;
      21     return 0;
      22 }
      哈哈哈你来打我啊
    3. 二分
       1 #include<iostream>
       2 using namespace std;
       3 int a[10010],x;
       4 int find(int x)
       5 {
       6     int l=1,r=n;
       7     while(l+1<r)
       8     {
       9         int mid=(l+r)/2;
      10         if(a[mid]==x)   return mid;
      11         if(a[mid]>x)    r=mid;
      12         if(a[mid]<x)    l=mid;
      13     }
      14     if(a[l]==x) return l;
      15     if(a[r]==x) return r;
      16     return -1;
      17 }
      18 int main()
      19 {
      20     cin>>x;
      21     cout<<find(x)<<endl;
      22     return 0;
      23 }
      哈哈哈你来打我啊
    4. quicksort
       1 /*
       2 Language:c++;
       3 By Kaike;
       4 Date:2016.09.25;
       5 */
       6 #include<iostream>
       7 using namespace std;
       8 int n,a[10010];
       9 void quicksort(int l,int r)
      10 {
      11     if(l>r) return ;
      12     int t=a[l];
      13     int i=l,j=r;
      14     while(i!=j)
      15     {
      16         while(a[j]>=temp && i<j)
      17             j--;
      18         while(a[i]<=temp && i<j)
      19             i++;
      20         if(i<j)
      21             swap(a[i],a[j]);
      22     }
      23     a[l]=a[i];
      24     a[i]=temp;
      25     quicksort(l,i-1);
      26     wuicksort(i+1,right);
      27     return ;
      28 }
      29 int main()
      30 {
      31     cin>>n;
      32     for(int i=1;i<=n;i++)
      33         cin>>a[i];
      34     quicksort(1,n);
      35     for(int i=1;i<=n;i++)
      36         cout<<a[i];
      37     return 0;
      38 }
      哈哈哈你来打我啊
    No matter how you feel, get up , dress up , show up ,and never give up.
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  • 原文地址:https://www.cnblogs.com/Kaike/p/5905753.html
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