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比較簡單的題

並查集維護一下必須選擇的大小 也就是物品

然後0/1揹包處理指定體積能否組成

(一開始開bool想做一個傳遞真值就是D不出來....能有dalao講一下嗎)

Code:

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<queue>
 5 #define ms(a,b) memset(a,b,sizeof a)
 6 #define rep(i,a,n) for(int i = a;i <= n;i++)
 7
 
 #define per(i,n,a) for(int i = n;i >= a;i--)
 8 #define inf 1000000007
 9 using namespace std;
10 typedef long long ll;
11 typedef double D;
12 #define eps 1e-8
13 ll read() {
14     ll as = 0,fu = 1;
15     char c = getchar();
16     while(c < '0' || c > '9') {
17         if(c == '-') fu = -1;
18         c = getchar();
 
19     }
20     while(c >= '0' && c <= '9') {
21         as = as * 10 + c - '0';
22         c = getchar();
23     }
24     return as * fu;
25 }
26 //head
27 const int N = 100005;
28 int n,m,k;
29 
30 int pa[N],d[N];
31 int gpa(int x) {
32     if(pa[x] == x) return x;
33     return pa[x] = gpa(pa[x]);
 
34 }
35 int Merge(int x,int y) {
36     int fx = gpa(x),fy = gpa(y);
37     if(fx ^ fy) pa[fx] = fy,d[fy] += d[fx];
38 }
39 
40 int stk[N],top;
41 int dp[N<<1];
42 #define Abs(x) (((x)>(~(x)+1)) ? x : (~(x)+1))
43 int main() {
44     // freopen("in.in","r",stdin);
45     n = read(),m = read(),k = read();
46     rep(i,1,n) pa[i] = i,d[i] = 1;
47     rep(i,1,k) Merge(read(),read());
48     rep(i,1,n) if(pa[i] == i) stk[++top] = d[i];
49     rep(i,1,top) {
50         per(j,m<<1,stk[i]) {
51             dp[j] = max(dp[j],dp[j-stk[i]] + stk[i]);
52         }
53     }
54     int ans = inf,minn = inf;
55     rep(i,1,m<<1) {
56         if(minn > Abs(dp[i]-m)) minn = Abs(dp[i]-m),ans = dp[i];
57     }
58     printf("%d\n",ans == inf ? 0 : ans);
59     return 0;
60 }