Hdu2473-junk-mail Filter deletes and sets nodes using a virtual array

Hdu2473-junk-mail filter:http://acm.hdu.edu.cn/showproblem.php?pid=2473

The main topic: M a B, representing A and b are the same class, S A, representing the original given the information of a is wrong, and now separate it into a category. Ask for the last number of messages in total.

If it's just a classification, it's very straightforward to think about it and look it up. But if you use and check the set directly there will be a mistake, because the deleted node may also have other sub-nodes, if you delete it directly, the result will be wrong. Here you need to use a virtual array, trick, and the father array to achieve the purpose of "delete" (actually the node still exists).

Code:

#include <iostream> #include <cstring> #include <cstdio>using namespace std;const int maxn = 1000111*2;    int n,m;int X,y;int cnt,case = 0,ans;int trick[maxn],father[maxn],hash[maxn];void Initial () {cnt = N; Ans = 0;for (int i = 0;i < maxn;i++)//Open another virtual array Trick, start and Father store the same information father[i] = trick[i] = I,hash[i] = 0;} int Find (int x) {if (x = = Father[x]) return X;return father[x] = find (Father[x]);} void Union (int x,int y) {x = find (x); y = find (y); if (x! = y) father[y] = x;} void Delete (int x) {father[cnt] = cnt;//The information that is passed in is Trick, where the change does not affect the query of the child nodes of x trick[x] = cnt++;//updated information in Trick, delete x, The expression x becomes a single collection}char Op[5];int main () {while (~scanf ("%d%d", &n,&m), N + M) {Initial (), while (m--) {scanf ("%s", op); (op[0] = = ' M ') {scanf ("%d%d", &x,&y); Union (Trick[x],trick[y]);//pass in the information in the Trick, but find the merger with father, the information is stored in Trick, not destroyed}else{scanf ("%d", &x);D elete (x);//delete x node}}for (int i = 0;i < n;i++)//Only N humans are not changed, the lookup is divided into several sets {x = Find (Trick[i]); HASH[X]) hash[x] = 1,ans++;} printf ("Case #%d:%D\n ", ++case,ans);} return 0;}

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Hdu2473-junk-mail Filter deletes and sets nodes using a virtual array