https://ac.nowcoder.com/acm/contest/317/I

C++版本一

std

題解：啟發(fā)式合并

#include<cstdio> #include<algorithm> #include<cstring> #include<queue> #include<iostream> #include<ctime> #include<cmath> #include<set> #include<map> #define ll long long #define M 200010 using namespace std; int read() {int nm = 0, f = 1;char c = getchar();for(; !isdigit(c); c = getchar()) if(c == '-') f = -1;for(; isdigit(c); c = getchar()) nm = nm * 10 + c - '0';return nm * f; }int note[M], sz[M], cor[M], id[M]; vector<int>to[M], to1[M]; int n, q, ans; void dfs(int now, int fa) {if(cor[now] != 0 && cor[now] != cor[fa]) ans++;for(int i = 0; i < to[now].size(); i++) {int vj = to[now][i];if(vj == fa) continue;dfs(vj, now);} }void del(int x) {for(int i = 0; i < to[x].size(); i++) {int vj = to[x][i];if(cor[vj] != cor[x]) ans--;} } void insert(int x) {for(int i = 0; i < to[x].size(); i++) {int vj = to[x][i];if(cor[vj] != cor[x]) ans++;} } int tot = 0, tot2 = 0; int main() {n = read(), q = read();for(int i = 1; i <= n; i++) cor[i] = read(), sz[cor[i]]++, to1[cor[i]].push_back(i), id[i] = i, note[i] = i;for(int i = 1; i < n; i++) {int vi = read(), vj = read();to[vi].push_back(vj), to[vj].push_back(vi);}to[1].push_back(0), cor[0] = 0x3e3e3e3e;dfs(1, 0);while(q--) {int x = read(), y = read();int xn = id[x], yn = id[y];if(sz[xn] < sz[yn]) {tot += sz[xn], tot2 += to1[xn].size();for(int i = 0; i < to1[xn].size(); i++) {int op = to1[xn][i];del(op);to1[yn].push_back(op);}for(int i = 0; i < to1[xn].size(); i++) {int op = to1[xn][i];cor[op] = yn;}for(int i = 0; i < to1[xn].size(); i++) {int op = to1[xn][i];insert(op);}to1[xn].clear();sz[yn] += sz[xn];sz[xn] = 0;id[x] = 0;} else {tot+=sz[yn], tot2 += to1[yn].size();for(int i = 0; i < to1[yn].size(); i++) {int op = to1[yn][i];del(op);to1[xn].push_back(op);}for(int i = 0; i < to1[yn].size(); i++) {int op = to1[yn][i];cor[op] = xn;}for(int i = 0; i < to1[yn].size(); i++) {int op = to1[yn][i];insert(op);}to1[yn].clear();sz[xn] += sz[yn];sz[yn] = 0;id[y] = xn;id[x] = 0;}cout << ans << "\n";}return 0; }

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