树状数组模板 Tree Array

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这几天去浙江省选当垫底（Orz我是蒟蒻），然后顺便复习下树状数组

关于树状数组，其实很好理解，主要就是lowbit()操作的巧妙


其实树状数组自己写几个代码就很容易理解了，也可以参见这里（Km的小天地）

# include <iostream>
# include <stdio.h>
# include <string.h>
using namespace std;
int a[50010], c[50010], n, sum[50010]={};
int lowbit(int x) {return x&(-x);}
void mdf(int p, int del) {
while(p<=n) {
c[p]+=del;
p+=lowbit(p);
}
}
int ca(int dg) {
int r=0;
while(dg!=0) {
r+=c[dg];
dg-=lowbit(dg);
}
return r;
}
int main() {int T,ft;
scanf("%d", &T);ft=T;
while(T--) {
printf("Case %d:\n",ft-T);
scanf("%d", &n);
for (int i=1;i<=n;++i) {
scanf("%d", &a[i]);
sum[i]=sum[i-1]+a[i];
c[i]=sum[i]-sum[i-lowbit(i)];
}
//for (int i=1;i<=n;++i) printf("%d ", c[i]);
while(1) {
char st[10]; int ta,tb;
scanf("%s", st);
//printf("%s %d %d",st,ta,tb);
if (strcmp(st,"End")==0) break;
scanf("%d %d",&ta,&tb);
if (strcmp(st,"Add")==0) {
mdf(ta,tb);
}
else if (strcmp(st,"Sub")==0) {
mdf(ta,-1*tb);
}
else if (strcmp(st,"Query")==0) {
if(ta>tb) {int p=ta;ta=tb;tb=p;}
printf("%d\n",ca(tb)-ca(ta-1));
}
}}
return 0;
}

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好吧我暂时就写到这一题树状数组，果然我还是太弱了ORZ各位神犇们

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