线段树--区间更新-区间查询HDU 1698

题意： 给钩子的价值更新，给出区间，查找区间价值

思路：加lazy标记，不必更新到每个子节点 

#include <stdio.h>
#include <math.h>
#include <iostream>
#include <algorithm>
#define lson i<<1,left,mid
#define rson i<<1|1,mid+1,right
using namespace std;
struct TreeNode
{
    int lazy,val,left,right,tag;
} Tree[400005];
void Build(int i , int left , int right )
{
    Tree[i].lazy=0;
    Tree[i].left=left;
    Tree[i].right=right;
    Tree[i].tag=0;
    if(left==right)
    {
        Tree[i].val=1;
        return ;
    }
    int mid=(left+right)>>1;
    Build(lson);
    Build(rson);
    Tree[i].val=Tree[i<<1].val+Tree[i<<1|1].val;
}


void update(int i,int left, int right , int w)
{
    if(Tree[i].left==left && Tree[i].right ==right )
    {
        Tree[i].tag=w;
        Tree[i].lazy=1;
        Tree[i].val=w*(right - left +1);
        return ;
    }
    int mid=(Tree[i].left+Tree[i].right)>>1;
    if(Tree[i].lazy==1)
    {
        Tree[i].lazy=0;
        Tree[i<<1].lazy=Tree[i<<1|1].lazy=1;

        Tree[i<<1].tag=Tree[i].tag;
        Tree[i<<1|1].tag=Tree[i].tag;

        Tree[i<<1].val=(Tree[i<<1].right-Tree[i<<1].left+1)*Tree[i].tag;
        Tree[i<<1|1].val=(Tree[i<<1|1].right-Tree[i<<1|1].left+1)*Tree[i].tag;
        Tree[i].tag=0;
    }
    if(right<=mid)
    {
        update(i<<1,left,right,w);
    }
    else if(left>mid)
    {
        update(i<<1|1,left,right,w);
    }
    else
    {
        update(lson,w);
        update(rson,w);
    }
    Tree[i].val=Tree[i<<1].val+Tree[i<<1|1].val;
}
int main()
{
    int x,y,z;
    int n;
    int m;
    int T;
    scanf("%d",&T);
    int iCase=0;
    while(T--)
    {
        iCase++;
        scanf("%d%d",&n,&m);
        Build(1,1,n);
        while(m--)
        {
            scanf("%d%d%d",&x,&y,&z);
            update(1,x,y,z);
         }

        printf("Case %d: The total value of the hook is %d.\n",iCase,Tree[1].val);
    }
    return 0;
}