E

Think:
1知识点：线段树区间更新+lazy标记
2题意：在n个初始化点权为1的点的基础上进行区间更新，询问最终状态n个点的点权之和
3反思：当前题目lazy标记赋值更新

vjudge题目链接

以下为Wrong Answer代码——lazy标记更新错误

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N = 101400;struct Node{    int sum;}node[N<<2];int lazy[N<<2];void Build(int l, int r, int rt);void Updata(int rt);void down(int rt, int l, int r);void up_v(int L, int R, int v, int l, int r, int rt);int main(){    int T, k = 1, n, m, L, R, v;    scanf("%d", &T);    while(T--){        scanf("%d", &n);        Build(1, n, 1);        scanf("%d", &m);        while(m--){            scanf("%d %d %d", &L, &R, &v);            up_v(L, R, v, 1, n, 1);        }        printf("Case %d: The total value of the hook is %d.\n", k++, node[1].sum);    }    return 0;}void Build(int l, int r, int rt){    lazy[rt] = 0;    if(l == r){        node[rt].sum = 1;        return;    }    int mid = (l+r)/2;    Build(l, mid, rt<<1);    Build(mid+1, r, rt<<1|1);    Updata(rt);}void Updata(int rt){    node[rt].sum = node[rt<<1].sum + node[rt<<1|1].sum;}void up_v(int L, int R, int v, int l, int r, int rt){    if(L <= l && r <= R){        node[rt].sum = v*(r-l+1);        lazy[rt] = v;        return;    }    down(rt, l, r);    int mid = (l+r)/2;    if(L <= mid)        up_v(L, R, v, l, mid, rt<<1);    if(R > mid)        up_v(L, R, v, mid+1, r, rt<<1|1);    Updata(rt);}void down(int rt, int l, int r){    if(lazy[rt]){        lazy[rt<<1] += lazy[rt];        lazy[rt<<1|1] += lazy[rt];        int mid = (l+r)/2;        node[rt<<1].sum = lazy[rt]*(mid-l+1);        node[rt<<1|1].sum = lazy[rt]*(r-mid);        lazy[rt] = 0;    }}

以下为Accepted代码

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N = 101400;struct Node{    int sum;}node[N<<2];int lazy[N<<2];void Build(int l, int r, int rt);void Updata(int rt);void down(int rt, int l, int r);void up_v(int L, int R, int v, int l, int r, int rt);int main(){    int T, k = 1, n, m, L, R, v;    scanf("%d", &T);    while(T--){        scanf("%d", &n);        Build(1, n, 1);        scanf("%d", &m);        while(m--){            scanf("%d %d %d", &L, &R, &v);            up_v(L, R, v, 1, n, 1);        }        printf("Case %d: The total value of the hook is %d.\n", k++, node[1].sum);    }    return 0;}void Build(int l, int r, int rt){    lazy[rt] = 0;    if(l == r){        node[rt].sum = 1;        return;    }    int mid = (l+r)/2;    Build(l, mid, rt<<1);    Build(mid+1, r, rt<<1|1);    Updata(rt);}void Updata(int rt){    node[rt].sum = node[rt<<1].sum + node[rt<<1|1].sum;}void up_v(int L, int R, int v, int l, int r, int rt){    if(L <= l && r <= R){        node[rt].sum = v*(r-l+1);        lazy[rt] = v;        return;    }    down(rt, l, r);    int mid = (l+r)/2;    if(L <= mid)        up_v(L, R, v, l, mid, rt<<1);    if(R > mid)        up_v(L, R, v, mid+1, r, rt<<1|1);    Updata(rt);}void down(int rt, int l, int r){    if(lazy[rt]){        lazy[rt<<1] = lazy[rt];/*lazy标记赋值更新*/        lazy[rt<<1|1] = lazy[rt];/*lazy标记赋值更新*/        int mid = (l+r)/2;        node[rt<<1].sum = lazy[rt]*(mid-l+1);        node[rt<<1|1].sum = lazy[rt]*(r-mid);        lazy[rt] = 0;    }}