P1505 [国家集训队]旅游
哈!树剖+线段树的水题!
讲道理前面的那道“月下毛景树”已经把这种化边权为点权的考的淋漓尽致了。
特别在于这些题的码量
我早上就直接打了一遍,然后就美妙地WA了。
下午再随便地打一遍,突然明白了早上错了哪里。
重新摸一遍板子,交上去,A了。。。
把早上那个唯一写错的地方改了,交上去,也A了。。。
这个故事告诉我们细心写好当前的每一句代码是多么重要。
不然你就要调得心态爆炸了哦
这道题的线段树修改也简单,最大最小值互换后取相反数,区间和也取相反数就完事了。
代码:
#include<cstdio>
#include<algorithm>
#define ll long long
const ll maxn = 20005;
const ll INF = 0x3f3f3f3f;// ????????????????????????????///
struct Edges
{
ll next, to, weight, id;
} e[maxn << 1];
ll head[maxn], tot;
ll n, m;
//
ll dep[maxn], size[maxn], wson[maxn], fa[maxn], weight[maxn], id[maxn];
ll top[maxn], dfn[maxn], pre[maxn], dtot;
//
struct segTree
{
ll sum[maxn << 2], minv[maxn << 2], maxv[maxn << 2], lazy[maxn << 2];
#define lson (root << 1)
#define rson (root << 1 | 1)
void pushup(ll root)
{
sum[root] = sum[lson] + sum[rson];
minv[root] = std::min(minv[lson], minv[rson]);
maxv[root] = std::max(maxv[lson], maxv[rson]);
}
void pushdown(ll root)
{
if(lazy[root])
{
ll temp;
sum[lson] = -sum[lson];
temp = minv[lson];
minv[lson] = -maxv[lson];
maxv[lson] = -temp;
lazy[lson] ^= 1;
sum[rson] = -sum[rson];
temp = minv[rson];
minv[rson] = -maxv[rson];
maxv[rson] = -temp;
lazy[rson] ^= 1;
lazy[root] = 0;
}
}
void build(ll root, ll l, ll r)
{
lazy[root] = 0;
if(l == r) sum[root] = minv[root] = maxv[root] = weight[pre[l]];
else
{
ll mid = (l + r) >> 1;
build(lson, l, mid);
build(rson, mid + 1, r);
pushup(root);
}
}
void singal_update(ll root, ll l, ll r, ll p, ll k)
{
if(l == r) sum[root] = minv[root] = maxv[root] = k;
else
{
pushdown(root);
ll mid = (l + r) >> 1;
if(p <= mid) singal_update(lson, l, mid, p, k);
else singal_update(rson, mid + 1, r, p, k);
pushup(root);
}
}
void interval_update(ll root, ll l, ll r, ll x, ll y)
{
if(r < x || y < l) return;
if(x <= l && r <= y)
{
sum[root] = -sum[root];
ll temp = minv[root];
minv[root] = -maxv[root];
maxv[root] = -temp;
lazy[root] ^= 1;
return;
}
pushdown(root);
ll mid = (l + r) >> 1;
interval_update(lson, l, mid, x, y);
interval_update(rson, mid + 1, r, x, y);
pushup(root);
}
ll querysum(ll root, ll l, ll r, ll x, ll y)
{
if(r < x || y < l) return 0;
if(x <= l && r <= y) return sum[root];
pushdown(root);
ll mid = (l + r) >> 1;
return querysum(lson, l, mid, x, y) + querysum(rson, mid + 1, r, x, y);
}
ll querymin(ll root, ll l, ll r, ll x, ll y)
{
if(r < x || y < l) return INF;
if(x <= l && r <= y) return minv[root];
pushdown(root);
ll mid = (l + r) >> 1;
return std::min(querymin(lson, l, mid, x, y), querymin(rson, mid + 1, r, x, y));
}
ll querymax(ll root, ll l, ll r, ll x, ll y)
{
if(r < x || y < l) return -INF;
if(x <= l && r <= y) return maxv[root];
pushdown(root);
ll mid = (l + r) >> 1;
return std::max(querymax(lson, l, mid, x, y), querymax(rson, mid + 1, r, x, y));
}
} seg;
ll read()
{
ll ans = 0, s = 1;
char ch = getchar();
while(ch > '9' || ch < '0'){ if(ch == '-') s = -1; ch = getchar(); }
while(ch >= '0' && ch <= '9') ans = ans * 10 + ch - '0', ch = getchar();
return s * ans;
}
void link(ll u, ll v, ll w, ll i)
{
e[++tot] = (Edges){head[u], v, w, i};
head[u] = tot;
}
void dfs1(ll u, ll f)
{
dep[u] = dep[f] + 1; fa[u] = f; size[u] = 1;
for(ll i = head[u]; i; i = e[i].next)
{
ll v = e[i].to;
if(v == f) continue;
dfs1(v, u);
size[u] += size[v];
weight[v] = e[i].weight;
id[e[i].id] = v;
if(size[v] > size[wson[u]]) wson[u] = v;
}
}
void dfs2(ll u, ll topf)
{
top[u] = topf; dfn[u] = ++dtot; pre[dtot] = u;
if(wson[u]) dfs2(wson[u], topf);
for(ll i = head[u]; i; i = e[i].next)
{
ll v = e[i].to;
if(v == fa[u] || v == wson[u]) continue;
dfs2(v, v);
}
}
void N(ll u, ll v)
{
while(top[u] != top[v])
{
if(dep[top[u]] < dep[top[v]]) std::swap(u, v);
seg.interval_update(1, 1, n, dfn[top[u]], dfn[u]);
u = fa[top[u]];
}
if(dep[u] > dep[v]) std::swap(u, v);
seg.interval_update(1, 1, n, dfn[u] + 1, dfn[v]);
}
ll SUM(ll u, ll v)
{
ll ans = 0;
while(top[u] != top[v])
{
if(dep[top[u]] < dep[top[v]]) std::swap(u, v);
ans += seg.querysum(1, 1, n, dfn[top[u]], dfn[u]);
u = fa[top[u]];
}
if(dep[u] > dep[v]) std::swap(u, v);
ans += seg.querysum(1, 1, n, dfn[u] + 1, dfn[v]);
return ans;
}
ll MAX(ll u, ll v)
{
ll ans = -INF;
while(top[u] != top[v])
{
if(dep[top[u]] < dep[top[v]]) std::swap(u, v);
ans = std::max(ans, seg.querymax(1, 1, n, dfn[top[u]], dfn[u]));
u = fa[top[u]];
}
if(dep[u] > dep[v]) std::swap(u, v);
ans = std::max(ans, seg.querymax(1, 1, n, dfn[u] + 1, dfn[v]));
return ans;
}
ll MIN(ll u, ll v)
{
ll ans = INF;
while(top[u] != top[v])
{
if(dep[top[u]] < dep[top[v]]) std::swap(u, v);
ans = std::min(ans, seg.querymin(1, 1, n, dfn[top[u]], dfn[u]));
u = fa[top[u]];
}
if(dep[u] > dep[v]) std::swap(u, v);
ans = std::min(ans, seg.querymin(1, 1, n, dfn[u] + 1, dfn[v]));
return ans;
}
int main()
{
n = read();
for(int i = 1; i < n; i++)
{
int u = read(), v = read(), w = read();
link(u + 1, v + 1, w, i); link(v + 1, u + 1, w, i);
}
dfs1(1, 0); dfs2(1, 1);
seg.build(1, 1, n);
m = read();
char opt[10];
while(m--)
{
scanf("%s", opt); ll u = read(), v = read();
if(opt[0] == 'C')
{
seg.singal_update(1, 1, n, dfn[id[u]], v);
}
else if(opt[0] == 'N')
{
N(u + 1, v + 1);
}
else if(opt[0] == 'S')
{
printf("%lld\n", SUM(u + 1, v + 1));
}
else if(opt[1] == 'A')
{
printf("%lld\n", MAX(u + 1, v + 1));
}
else if(opt[1] == 'I')
{
printf("%lld\n", MIN(u + 1, v + 1));
}
}
return 0;
}