hdu 5758(dp)

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pair
#include <bits/stdc++.h>using namespace std;#define LL long long#define pii pair<int, int>#define MP make_pair#define ls i << 1#define rs ls | 1#define md (ll + rr >> 1)#define lson ll, md, ls#define rson md + 1, rr, rs#define mod 1000000007#define inf 0x3f3f3f3f#define N 100010#define M 200020int fst[N], vv[M], nxt[M], e;pii p[N][3];int n;pii operator + (const pii &a, const pii &b){    return MP(a.first + b.first, a.second + b.second);}void init(){    memset(fst, -1, sizeof fst); e = 0;}void add(int u, int v){    vv[e] = v, nxt[e] = fst[u], fst[u] = e++;}void dfs(int u, int fa){    for(int i = 0; i < 3; ++i) p[u][i] = MP(0, 0);    pii tmp[3];    for(int i = fst[u]; ~i; i = nxt[i]){        int v = vv[i];        if(v == fa) continue;        dfs(v, u);        for(int j = 0; j < 3; ++j) tmp[j] = MP(inf, inf);        tmp[0] = min(tmp[0], p[u][1] + p[v][1] + MP(1, 1));        tmp[0] = min(tmp[0], p[u][2] + p[v][2] + MP(2, 2));        tmp[1] = min(tmp[1], tmp[0]);        tmp[1] = min(tmp[1], p[u][0] + p[v][1] + MP(0, 1));        tmp[1] = min(tmp[1], p[u][1] + p[v][2] + MP(1, 2));        tmp[1] = min(tmp[1], p[u][2] + p[v][1] + MP(1, 1));        tmp[2] = min(tmp[1], tmp[2]);        tmp[2] = min(tmp[2], p[u][0] + p[v][2] + MP(0, 2));        tmp[2] = min(tmp[2], p[u][1] + p[v][1] + MP(0, 1));        tmp[2] = min(tmp[2], p[u][2] + p[v][2] + MP(1, 2));        for(int j = 0; j < 3; ++j)            p[u][j] = tmp[j];    }}int main(){    int cas;    scanf("%d", &cas);    while(cas--){        scanf("%d", &n);        init();        for(int i = 1; i < n; ++i){            int u, v;            scanf("%d%d", &u, &v);            add(u, v);            add(v, u);        }        dfs(1, -1);        printf("%d\n", p[1][0].second);    }    return 0;}
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