树状数组

一维的情况

#include <iostream>using namespace std;int a[10000];//原始数据数组int c[10000];//树状数组int N;int lowbit(int n){return n&(-n);}void modify(int n,int delta){while(n <= N){c[n]+=delta;n+=lowbit(n);}}int sum(int n){int result=0;while(n!=0){result+=c[n];n-=lowbit(n);}return result;}int main(){while(cin>>N){for(int i=1;i<=N;i++){scanf("%d",&a[i]);modify(i,a[i]);}while(1){int k;cin>>k;cout<<sum(k)<<endl;}}}

二维情况

#include <iostream>using namespace std;int a[1000][1000];//原始数据数组int c[1000][1000];//树状数组int N;int lowbit(int n){return n&(-n);}void modify(int x,int y,int delta){for(int i=x;i<=N;i+=lowbit(i))for(int j=y;j<=N;j+=lowbit(j))c[i][j]+=delta;}int sum(int x,int y){int result=0;for(int i=x;i>0;i-=lowbit(i))for(int j=y;j>0;j-=lowbit(j))result+=c[i][j];return result;}int main(){while(cin>>N){memset(a,0,sizeof(a));memset(c,0,sizeof(c));for(int i=1;i<=N;i++)for(int j=1;j<=N;j++){scanf("%d",&a[i][j]);modify(i,j,a[i][j]);}while(1){int x,y;cin>>x>>y;cout<<sum(x,y)<<endl;}}}