BZOJ3155: Preprefix sum

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\n",(x+1)*sum(0,x)-sum(1,x));
 96         }
 97     }
 98 
 99     return 0;
100 
101 }
View Code

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

posted @ 2014-12-19 10:45  ZYF-ZYF  Views(200)  Comments(0)  Edit  收藏  举报