HDU 3974 Assign the task(线段树)

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#include <iostream>#include <cstring>#include <cstdlib>#include <cstdio>#include <cmath>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#define ll long longusing namespace std;const int MAXN = 50000 + 10;struct Edge{    int to, next;}edge[MAXN];int head[MAXN], tot;int S[MAXN], E[MAXN];int n;void init(){    memset(head, -1, sizeof(head));    tot = 0;    n = 0;}void AddEdge(int u, int v){    edge[tot].to = v;    edge[tot].next = head[u];    head[u] = tot++;}void dfs(int u){    S[u] = ++n;    for(int i=head[u];i!=-1;i=edge[i].next)    {        dfs(edge[i].to);    }    E[u] = n;}int vis[MAXN];struct Tree{    int l, r;    int val;    int lazy;}tree[MAXN<<2];void pushdown(int rt){    if(tree[rt].lazy)    {        tree[rt<<1].val = tree[rt].val;        tree[rt<<1|1].val = tree[rt].val;        tree[rt<<1].lazy = 1;        tree[rt<<1|1].lazy = 1;        tree[rt].lazy = 0;    }}void build(int l, int r, int rt){    tree[rt].l = l;    tree[rt].r = r;    tree[rt].val = -1;    tree[rt].lazy = 0;    if(l == r) return ;    int m = (l + r) >> 1;    build(l, m, rt<<1);    build(m + 1, r, rt<<1|1);}void update(int l, int r, int val, int rt){    if(tree[rt].l == l && tree[rt].r == r)    {        tree[rt].val = val;        tree[rt].lazy = 1;        return ;    }    pushdown(rt);    int m = (tree[rt].l + tree[rt].r) >> 1;    if(r <= m) update(l, r, val, rt<<1);    else if(l > m) update(l, r, val, rt<<1|1);    else    {        update(l, m, val, rt<<1);        update(m + 1, r, val, rt<<1|1);    }}int Query(int p, int rt){    if(tree[rt].l == p && tree[rt].r == p)    {        return tree[rt].val;    }    pushdown(rt);    int m = (tree[rt].l + tree[rt].r) >> 1;    if(p <= m) return Query(p, rt<<1);    else return Query(p, rt<<1|1);}int main(){    int N, T, kcase = 1;    scanf("%d", &T);    while(T--)    {        printf("Case #%d:\n", kcase++);        init();        scanf("%d", &N);        int u, v;        memset(vis, 0, sizeof(vis));        for(int i=1;i<N;i++)        {            scanf("%d%d", &u, &v);            vis[u] = 1;            AddEdge(v, u);        }        for(int i=1;i<=N;i++)        {            if(!vis[i])            {                dfs(i);                break;            }        }        build(1, N, 1);        int m = 0;        scanf("%d", &m);        char op[10];        while(m--)        {            scanf("%s", op);            if(op[0] == 'C')            {                scanf("%d", &u);                //cout << S[u] << endl;                printf("%d\n", Query(S[u], 1));            }            else            {                scanf("%d%d", &u, &v);                update(S[u], E[u], v, 1);            }        }    }    return 0;}
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