Tree array templates

Tree array templates

Tree arrays are much more efficient in the process of adding single points and summing up intervals than in the line tree. Therefore, it is necessary to learn (personal opinion)

Lowbit: I & (-I)

You can use add directly for single-point addition. If there are other operations, you can write another function.

For the sum, you can directly use summax minus the summin-1 to obtain the range and ratio, the Code complexity is much lower than the line segment tree.

Take Luogu 3374 as an example: http://daniu.luogu.org/problem/show? Pid = 3374 # sub

 1 #include<iostream> 2 #include<algorithm> 3 #include<string> 4 using namespace std; 5 #define MAX 500000 6 int N,M; 7 int a[MAX],c[MAX]; 8 //====================================================== 9 void init();//10 void ADD(int ,int );//11 int sum(int );12 //======================================================13 void ADD(int x,int y)14 {15    for(int i=x;i<=N;i+=i&(-i)  ){16       c[i]+=y;17    }18 }19 //======================================================20 int sum(int x)21 {22    int SUM=0;23    for(int i=x;i>=1;i-=i&(-i))24       SUM+=c[i];25    return SUM;26 }27 //======================================================28 void init()29 {30    int aa,bb,cc;31    cin>>N>>M;32    for(int i=1;i<=N;i++){33       cin>>a[i];34       ADD( i , a[i] );35    }36    for(int i=1;i<=M;i++){37       cin>>aa>>bb>>cc;38       if(aa==1)ADD(bb,cc);39       if(aa==2)cout<<sum(cc)-sum(bb-1)<<endl;40    }41 }42 //======================================================43 int main()44 {45   init();46    return 0 ;47 }