HDU 1698 Just a Hook（线段树）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1698

题目思路：区间修改，区间查询，线段树简单题

代码：

#include<cstdio>
#include<cmath>
#include<cstring>
#include<string>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<queue>
#include<stack>
#include<map>

using namespace std;

#define FOU(i,x,y) for(int i=x;i<=y;i++)
#define FOD(i,x,y) for(int i=x;i>=y;i--)
#define MEM(a,val) memset(a,val,sizeof(a))
#define PI acos(-1.0)

const double EXP = 1e-9;
typedef long long ll;
typedef unsigned long long ull;
const int INF = 0x3f3f3f3f;
const ll MINF = 0x3f3f3f3f3f3f3f3f;
const double DINF = 0xffffffffffff;
const int mod = 1e9+7;
const int N = 1e6+5;

int n;

struct node{
    int lft,rht;
    int lazy;
    int sum;
}segTree[N*4];

void pushUp(int id){
    segTree[id].sum = segTree[id*2].sum+segTree[id*2+1].sum;
}

void pushDown(int id){
    if(segTree[id].lazy){
        segTree[id*2].sum = (segTree[id*2].rht-segTree[id*2].lft+1)*segTree[id].lazy;
        segTree[id*2+1].sum = (segTree[id*2+1].rht-segTree[id*2+1].lft+1)*segTree[id].lazy;
        segTree[id*2].lazy = segTree[id].lazy;
        segTree[id*2+1].lazy = segTree[id].lazy;
        segTree[id].lazy=0;
    }
}

void build(int id,int l,int r){
    segTree[id].lft=l, segTree[id].rht=r;
    segTree[id].sum=0, segTree[id].lazy=0;
    if(l==r)
        segTree[id].sum=1;
    else{
        int mid = (l+r)>>1;
        build(id*2,l,mid);
        build(id*2+1,mid+1,r);
        pushUp(id);
    }
}

void upDate(int id,int l,int r,int val){
    if(l<=segTree[id].lft&&r>=segTree[id].rht){
        segTree[id].sum = (segTree[id].rht-segTree[id].lft+1)*val;
        segTree[id].lazy = val;
    }
    else{
        pushDown(id);
        int mid = (segTree[id].lft+segTree[id].rht)>>1;
        if(r<=mid)
            upDate(id*2,l,r,val);
        else if(l>=mid+1)
            upDate(id*2+1,l,r,val);
        else{
            upDate(id*2,l,r,val);
            upDate(id*2+1,l,r,val);
        }
        pushUp(id);
    }
}

int query(int id,int l,int r){
    int ans = 0;
    if(l<=segTree[id].lft&&r>=segTree[id].rht)
        return segTree[id].sum;
    pushDown(id);
    int mid = (segTree[id].lft+segTree[id].rht)>>1;
    if(r<=mid)
        ans += query(id*2,l,r);
    else if(l>=mid+1)
        ans += query(id*2+1,l,r);
    else{
        ans += query(id*2,l,r);
        ans += query(id*2+1,l,r);
    }
    return ans;
}

int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    std::ios::sync_with_stdio(false);
    int t,l,r,z,q,cnt=0;
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        build(1,1,n);
        scanf("%d",&q);
        while(q--){
            scanf("%d%d%d",&l,&r,&z);
            upDate(1,l,r,z);
        }
        cnt++;
        printf("Case %d: The total value of the hook is %d.\n",cnt,query(1,1,n));
    }
    return 0;
}