树状数组 统计序列中在元素左边比该元素小的元素个数

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统计序列中在元素左边比该元素小的元素个数

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#include<bits/stdc++.h>
#define MAX 100
using namespace std;
#define lowbit(i) ((i)&(-i))
//覆盖范围 
int c[MAX];
int n;
void update(int x,int v){
	for(int i=x;i<=n;i+=lowbit(i)){
		c[i]+=v;
	}
}
int getSum(int x){
	int sum=0;
	for(int i=x;i>0;i-=lowbit(i))
	{
		sum+=c[i];
	}
	return sum;
}

int main(){
	cin>>n;
	int x;
	memset(c,0,sizeof(c));
	int num=0;
	for(int i=1;i<=n;i++){
		cin>>x;
		update(x,1);//x出现次数+1 
		int t=getSum(x-1);
		num+=t;
		cout<<"第"<<i<<"位左边比它小的数的个数"<<t<<endl;
	} 
	cout<<"sum:"<<num<<endl;

	
	
}

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