poj3468A Simple Problem with Integers

線段樹的應用，注意處理更新的情況，不能單個處理，不然會超時！

#include<iostream>
#include<stdio.h>
#include<cstring>
using namespace std;

struct e{
    int left,right;
    long long add;
    long long sum;
};

e tree[400011];
long long a[100001];

long long build(int s,int t,int num){
    long long i,j;
    tree[num].left=s;
    tree[num].right=t;
    tree[num].add=0;
    if(s!=t)
    {
        i=build(s,(s+t)/2,num*2);
        j=build((s+t)/2+1,t,num*2+1);
    }
    else
    {
        tree[num].sum=a[s];
        return(a[s]);
    }
    tree[num].sum=i+j;
    return(tree[num].sum);
}

void insert(int s,int t,int add,int num){

    if(s<=tree[num].left&&tree[num].right<=t)
    {
        tree[num].add+=add;
        tree[num].sum+=add*(tree[num].right-tree[num].left+1);
        return;
    }
    if(tree[num].add){
        tree[num*2].sum+=tree[num].add*(tree[num*2].right-tree[num*2].left+1);
        tree[num*2+1].sum+=tree[num].add*(tree[num*2+1].right-tree[num*2+1].left+1);
        tree[num*2].add+=tree[num].add;
        tree[num*2+1].add+=tree[num].add;
        tree[num].add=0;
    }
    if(s<=(tree[num].left+tree[num].right)/2)
        insert(s,t,add,num*2);
    if(t>(tree[num].left+tree[num].right)/2)
        insert(s,t,add,num*2+1);
    tree[num].sum=tree[num*2].sum+tree[num*2+1].sum;

}

long long search(int s,int t,int num){
    long long i=0,j=0;
    if(s<=tree[num].left&&tree[num].right<=t)
    {
        return(tree[num].sum);
    }
    if(tree[num].add){
        tree[num*2].sum+=tree[num].add*(tree[num*2].right-tree[num*2].left+1);
        tree[num*2+1].sum+=tree[num].add*(tree[num*2+1].right-tree[num*2+1].left+1);
        tree[num*2].add+=tree[num].add;
        tree[num*2+1].add+=tree[num].add;
        tree[num].add=0;
    }
    if(s<=(tree[num].left+tree[num].right)/2)
    {
        i=search(s,t,num*2);

    }
    if(t>(tree[num].left+tree[num].right)/2)
    {
        j=search(s,t,num*2+1);

    }

    return(i+j);
}


int main(){
    int i,j,k,n,m,p,t;
    char s;
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
        scanf("%lld",&a[i]);
    build(1,n,1);
    for(i=1;i<=m;i++)
    {
        scanf("\n%c",&s);
        if(s=='C')
        {
            scanf("%d%d%d",&j,&k,&p);
            if(j>k) {t=j;j=k;k=t;}
            insert(j,k,p,1);
        }
        else
        {
            scanf("%d%d",&j,&k);
            if(j>k) {t=j;j=k;k=t;}
            cout<<search(j,k,1)<<endl;
        }
    }

    return(0);
}