hdu1698 区间更新

初写线段树的时候，印象最深的一道，有一个pushdown的操作，使我的tle变成了ac

题意

输入t，然后t组数据

输入n，m，n代表n个点上价值全是1的绳子，m代表m次操作

m行l，r，val  就是区间l，r变成val

求最后绳子总共价值

思路

线段树，懒人标记

 #include<queue>
 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<map>
 #include<cmath>
 #include<string>
 #include<vector>
 #include<functional>
 #define inf 0x3f3f3f3f
 #define mem(k,b) memset(k,b,sizeof(k))
 #define ll long long
 #define ls (x)<<1
 #define rs (x)<<1|1
 #define lson ls,l,mid
 #define rson rs,mid+1,r
 using namespace std;
 const int maxn = ;

 int t, n, m, q, p, z;
 int tree[maxn << ], add[maxn << ];

 void pushup(int x) {
     tree[x] = tree[ls] + tree[rs];
     return;
 }

 void pushdown(int x, int len){
     if (add[x]){
         add[ls] = add[x];
         add[rs] = add[x];
         tree[ls] = add[x] * (len - (len >> ));
         tree[rs] = add[x] * (len >> );
         add[x] = ;
     }
 }

 void build(int x, int l, int r){
     add[x] = ;
     if (l == r){
         tree[x] = ;
         return;
     }
     int mid = (l + r) >> ;
     build(lson); build(rson);
     pushup(x);
 }

 void xiugai(int x, int l, int r, int l1, int r1,int zhi1){
     if (l >= l1 && r<=r1){
         add[x] = zhi1;
         tree[x] = zhi1*(r - l + );
         return;
     }
     pushdown(x, r - l + );
     int mid = (l + r) >> ;
     if (r1<= mid){
         xiugai(lson, l1, r1, zhi1);
     }
     else if (l1>mid){
         xiugai(rson, l1, r1, zhi1);
     }
     else{
         xiugai(lson, l1, mid, zhi1);
         xiugai(rson, mid + , r1, zhi1);
     }
     pushup(x);
 }

 int main(){
     int c = ;
     scanf("%d",&t);
     while (t--){
         scanf("%d%d",&n,&m);
         build(, , n);
         for (int i = ; i < m; i++){
             scanf("%d%d%d",&q,&p,&z);
             xiugai(, , n, q, p, z);
         }
         printf("Case %d: The total value of the hook is %d.\n",c++,tree[]);
     }
     return ;
 }