hdu 5274(树链剖分)

解题思路：这道题据说是树链剖分，所以也学习了一下。

http://blog.sina.com.cn/s/blog_7a1746820100wp67.html

不同的是这里是点权值，我按照相似的处理方式，不知道为什么WA了。。。调了好久。。

#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int maxn = 100005;struct Segment{int l,r,sum;}tree[maxn<<2];struct Edge{int to,next;}edge[maxn<<1];int A[maxn],son[maxn],top[maxn],w[maxn];int dep[maxn],fa[maxn],size[maxn];int cnt,num,pre[maxn];int n,q,idx[maxn];void addedge(int u,int v){edge[cnt].to = v;edge[cnt].next = pre[u];pre[u] = cnt++;}void dfs(int u){size[u] = 1;son[u] = 0;int tmp = 0;for(int i = pre[u]; i != -1; i = edge[i].next){int v = edge[i].to;if(fa[u] == v) continue;fa[v] = u;dep[v] = dep[u] + 1;dfs(v);size[u] += size[v];if(size[v] > tmp){tmp = size[v];son[u] = v;}}}void build_tree(int u,int tp){w[u] = ++num; top[u] = tp; idx[num] = u;if(son[u] != 0) build_tree(son[u],tp);for(int i = pre[u]; i != -1; i = edge[i].next){int v = edge[i].to;if(v == son[u] || fa[u] == v) continue;build_tree(v,v);}}void build_Segment(int rt,int l,int r){tree[rt].l = l, tree[rt].r = r;tree[rt].sum = 0;if(l == r) return;int mid = (l + r) >> 1;build_Segment(rt<<1,l,mid);build_Segment(rt<<1|1,mid+1,r);}void update(int rt,int pos,int val){if(tree[rt].l == tree[rt].r){tree[rt].sum = val;return;}int mid = (tree[rt].l + tree[rt].r) >> 1;if(pos <= mid) update(rt<<1,pos,val);else update(rt<<1|1,pos,val);tree[rt].sum = tree[rt<<1].sum ^ tree[rt<<1|1].sum;}int query(int rt,int l,int r){if(l <= tree[rt].l && tree[rt].r <= r)return tree[rt].sum;int mid = (tree[rt].l + tree[rt].r) >> 1;int ans = 0;if(l <= mid) ans ^= query(rt<<1,l,r);if(mid < r) ans ^= query(rt<<1|1,l,r);return ans;}int find(int l,int r){int f1 = top[l], f2 = top[r];int ans = 0;while(f1 != f2){if(dep[f1] < dep[f2]){swap(f1,f2);swap(l,r);}ans ^= query(1,w[f1],w[l]);l = fa[f1], f1 = top[l];}if(l == r) return ans^A[f1];if(dep[l] > dep[r]) swap(l,r);return ans ^= query(1,w[son[l]],w[r])^A[f1];}int main(){int t,u,v,op;scanf("%d",&t);while(t--){scanf("%d%d",&n,&q);memset(pre,-1,sizeof(pre));cnt = num = 0;for(int i = 1; i < n; i++){scanf("%d%d",&u,&v);addedge(u,v);addedge(v,u);}dep[1] = 0;dfs(1);build_tree(1,1);build_Segment(1,1,num);for(int i = 1; i <= n; i++){scanf("%d",&A[i]);A[i]++;update(1,w[i],A[i]);}for(int i = 1; i <= q; i++){scanf("%d%d%d",&op,&u,&v);if(op == 0){A[u] = v + 1;update(1,w[u],A[u]);}else {int ans = find(u,v);printf("%d\n",ans-1);}}}return 0;}

PS:今天早上把这道题给A了，参考了一下别人的代码，发现自己的代码不一样的地方就是在find函数里，我是按照边更新的方式去写的，而这道题是点更新。关键是最后f1=f2后，如何把根节点加入进去。但仔细想想还是没明白我的为什么错了。

#include<iostream>#include<cstdio>#include<cstring>using namespace std;const int maxn = 100005;struct Segment{int l,r,sum;}tree[maxn<<2];struct Edge{int to,next;}edge[maxn<<1];int A[maxn],son[maxn],top[maxn],w[maxn];int dep[maxn],fa[maxn],size[maxn];int cnt,num,pre[maxn];int n,q;void addedge(int u,int v){edge[cnt].to = v;edge[cnt].next = pre[u];pre[u] = cnt++;}void dfs(int u){size[u] = 1;son[u] = 0;int tmp = 0;for(int i = pre[u]; i != -1; i = edge[i].next){int v = edge[i].to;if(fa[u] == v) continue;fa[v] = u;dep[v] = dep[u] + 1;dfs(v);size[u] += size[v];if(size[v] > tmp){tmp = size[v];son[u] = v;}}}void build_tree(int u,int tp){w[u] = ++num; top[u] = tp;if(son[u] != 0) build_tree(son[u],tp);for(int i = pre[u]; i != -1; i = edge[i].next){int v = edge[i].to;if(v == son[u] || fa[u] == v) continue;build_tree(v,v);}}void build_Segment(int rt,int l,int r){tree[rt].l = l, tree[rt].r = r;tree[rt].sum = 0;if(l == r) return;int mid = (l + r) >> 1;build_Segment(rt<<1,l,mid);build_Segment(rt<<1|1,mid+1,r);}void update(int rt,int pos,int val){if(tree[rt].l == tree[rt].r){tree[rt].sum = val;return;}int mid = (tree[rt].l + tree[rt].r) >> 1;if(pos <= mid) update(rt<<1,pos,val);else update(rt<<1|1,pos,val);tree[rt].sum = tree[rt<<1].sum ^ tree[rt<<1|1].sum;}int query(int rt,int l,int r){if(l <= tree[rt].l && tree[rt].r <= r)return tree[rt].sum;int mid = (tree[rt].l + tree[rt].r) >> 1;int ans = 0;if(l <= mid) ans ^= query(rt<<1,l,r);if(mid < r) ans ^= query(rt<<1|1,l,r);return ans;}int find(int l,int r){int f1 = top[l], f2 = top[r];int ans = 0;while(f1 != f2){if(dep[f1] < dep[f2]){swap(f1,f2);swap(l,r);}ans ^= query(1,w[f1],w[l]);l = fa[f1], f1 = top[l];}if(dep[l] > dep[r]) swap(l,r);<span style="white-space:pre"></span>//没有比较l与r，这是关键点return ans ^= query(1,w[l],w[r]);}int main(){int t,u,v,op;scanf("%d",&t);while(t--){scanf("%d%d",&n,&q);memset(pre,-1,sizeof(pre));cnt = num = 0;for(int i = 1; i < n; i++){scanf("%d%d",&u,&v);addedge(u,v);addedge(v,u);}dep[1] = 0;dfs(1);build_tree(1,1);build_Segment(1,1,num);for(int i = 1; i <= n; i++){scanf("%d",&A[i]);update(1,w[i],A[i]+1);}for(int i = 1; i <= q; i++){scanf("%d%d%d",&op,&u,&v);if(op == 0)update(1,w[u],v+1);else {int ans = find(u,v);printf("%d\n",ans-1);}}}return 0;}