题解：
写过树状数组搞区间修改和区间求和的就可以秒出吧。。。
代码：
1 #include<cstdio> 2 3 #include<cstdlib> 4 5 #include<cmath> 6 7 #include<cstring> 8 9 #include<algorithm> 10 11 #include<iostream> 12 13 #include<vector> 14 15 #include<map> 16 17 #include<set> 18 19 #include<queue> 20 21 #include<string> 22 23 #define inf 1000000000 24 25 #define maxn 200000+5 26 27 #define maxm 20000000+5 28 29 #define eps 1e-10 30 31 #define ll long long 32 33 #define pa pair<int,int> 34 35 #define for0(i,n) for(int i=0;i<=(n);i++) 36 37 #define for1(i,n) for(int i=1;i<=(n);i++) 38 39 #define for2(i,x,y) for(int i=(x);i<=(y);i++) 40 41 #define for3(i,x,y) for(int i=(x);i>=(y);i--) 42 43 #define mod 1000000007 44 45 using namespace std; 46 47 inline int read() 48 49 { 50 51 int x=0,f=1;char ch=getchar(); 52 53 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 54 55 while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();} 56 57 return x*f; 58 59 } 60 int n,m; 61 ll a[maxn],s[maxn][2]; 62 inline void add(int k,int x,ll y) 63 { 64 for(;x<=n;x+=x&(-x))s[x][k]+=y; 65 } 66 inline ll sum(int k,int x) 67 { 68 ll t=0; 69 for(;x;x-=x&(-x))t+=s[x][k]; 70 return t; 71 } 72 73 int main() 74 75 { 76 77 freopen("input.txt","r",stdin); 78 79 freopen("output.txt","w",stdout); 80 81 n=read();m=read(); 82 for1(i,n){ll x=a[i]=read();add(0,i,x);add(1,i,i*x);} 83 char ch[10]; 84 while(m--) 85 { 86 scanf("%s",ch); 87 if(ch[0]=='M') 88 { 89 ll x=read(),y=read(); 90 add(0,x,y-a[x]);add(1,x,x*(y-a[x])); 91 a[x]=y; 92 }else 93 { 94 ll x=read(); 95 printf("%lld ",(x+1)*sum(0,x)-sum(1,x)); 96 } 97 } 98 99 return 0; 100 101 }
题目：http://ch.ezoj.tk/contest/Katharon%20%EF%BC%831/Preprefix%20Sum
感觉bz上的题面怎么不一样。。。233