题意：
先给出一个数组，，然后有两个操作
S x y 把第x个数改成y
M x y计算x~y个数的和
思路：
普通的树状数组，但不知道为什么会莫名其妙的一直WA
#include <iostream>#include <stdio.h>#include <string.h>#include <stack>#include <queue>#include <map>#include <set>#include <vector>#include <math.h>#include <bitset>#include <algorithm>#include <climits>using namespace std;#define LS 2*i#define RS 2*i+1#define UP(i,x,y) for(i=x;i<=y;i++)#define DOWN(i,x,y) for(i=x;i>=y;i–)#define MEM(a,x) memset(a,x,sizeof(a))#define W(a) while(a)#define gcd(a,b) __gcd(a,b)#define LL long long#define N 5000005#define MOD 1000000007#define INF 0x3f3f3f3f#define EXP 1e-8#define lowbit(x) (x&-x)LL c[N];int a[N],n;LL sum(int x){LL ret = 0;while(x>0){ret+=c[x];x-=lowbit(x);}return ret;}void add(int x,int d){while(x<=n){c[x]+=d;x+=lowbit(x);}}int main(){int i,j,k,x,y,cas = 1;char str[10];scanf("%d",&n);while(n){printf("Case %d:\n",cas++);for(i = 1; i<=n; i++){scanf("%d",&a[i]);}MEM(c,0);for(i = 1;i<=n;i++){add(i,a[i]);}while(1){scanf("%s",str);if(!strcmp(str,"END")) break;if(str[0]=='M'){scanf("%d%d",&x,&y);LL ans = sum(y)-sum(x-1);printf("%lld\n",ans);}else if(str[0]=='S'){scanf("%d%d",&x,&y);add(x,y-a[x]);a[x] = y;}}scanf("%d",&n);if(n)printf("\n");}return 0;}
读书破万卷，下笔如有神。
