[FZYZOJ 1821] 一道果题

 1 #include<stdio.h>
 2 char B[1<<15],*S=B,*T=B;
 3 #define getc() (S==T&&(T=(S=B)+fread(B,1,1<<15,stdin),S==T)?0:*S++)
 4 int n,m,b[100001],c[100001],a[100001];
 5 int lowbit(int x) {return x&(-x);}
 6 int getint() {
 7     int x=0,f=1; char ch=getc();
 8     while(ch<‘0‘||ch>‘9‘) {if(ch==‘-‘) f=-1; ch=getc();}
 9     while(ch>=‘0‘&&ch<=‘9‘) {x=(x<<3)+(x<<1)+ch-‘0‘; ch=getc();}
10     return x*f;
11 }
12 void modify(int x,int delta) {
13     while(x<=n) {
14         c[x]+=delta;
15         x+=lowbit(x);
16     }
17 } 
18 int cal(int x) {
19     int ret=0;
20     while(x!=0) {
21         ret+=c[x];
22         x-=lowbit(x);
23     }
24     return ret;
25 }
26 main() {
27     n=getint();m=getint();
28     for (int i=1;i<=n;++i) {
29         b[i]=getint();
30         a[i]=b[i]+a[i-1];
31         c[i]=a[i]-a[i-lowbit(i)];
32     }
33     while(m--) {
34         char ch=getc();
35         if(ch==‘Q‘) {
36             int p,q;p=getint();q=getint();
37             printf("%d\n",cal(q)-cal(p-1));
38         }
39         if(ch==‘M‘) {
40             int p,q;p=getint();q=getint();
41             int delta=q-b[p]; b[p]=q;
42             modify(p,delta);
43         }
44     }
45 }