树状数组

Posted 2020-09-18 bennettz

c为树状数组，c[i]存储i-lowbit[i]+1到i的数组的值

c[x+ lowbit(x)]为c[x]的父亲节点

http://cogs.pro/cogs/problem/problem.php?pid=264

/****************************************************************************************************

                                            树状数组 
                        

********************************************************************************************************/
#include<cstdio>
const int N = 100000;
int c[100005];//c为树状数组 
int lowbit(int x){
    return x&(-x);
}
void add(int x,int num){
    while(x<=N){
        c[x]+=num;
        x+=lowbit(x);//x+ lowbit(x)为x的父亲节点 
    }
}
int sum(int x){
    int ans=0;
    while(x){
        ans+=c[x];
        x-=lowbit(x);//c[i]存储i-lowbit[i]+1到i的数组的值，所以求前缀和要不断去掉最后一位 
    }
    return ans;
}
int main(){
    freopen("shulie.in","r",stdin);
    freopen("shulie.out","w",stdout);
    int n,m,x,a,b;
    char s[5];
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&x);
        add(i,x);
    }
    scanf("%d",&m);
    for(int i=0;i<m;i++){
        scanf("%s%d%d",s,&a,&b);
        if(s[0]==\'S\')printf("%d\\n",sum(b)-sum(a-1));
        else add(a,b);
    }
    return 0;
}