Create 5886_u012015746.cpp

From http://blog.csdn.net/u012015746/article/details/52567223

HDOJ/5886_u012015746.cpp

@@ -0,0 +1,138 @@
+#pragma comment(linker, "/STACK:102400000,102400000")
+#include <cstdio>
+#include <iostream>
+#include <cstdlib>
+#include <cstring>
+#include <algorithm>
+#include <cmath>
+#include <cctype>
+#include <map>
+#include <set>
+#include <queue>
+#include <bitset>
+#include <string>
+#include <complex>
+using namespace std;
+typedef pair<int,int> Pii;
+typedef long long LL;
+typedef unsigned long long ULL;
+typedef double DBL;
+typedef long double LDBL;
+#define MST(a,b) memset(a,b,sizeof(a))
+#define CLR(a) MST(a,0)
+#define SQR(a) ((a)*(a))
+#define PCUT puts("\n----------")
+
+const int maxn=1e5+10;;
+struct Graph
+{
+    int ndn, edn, last[maxn];
+    int u[2*maxn], v[2*maxn], w[2*maxn], nxt[2*maxn];
+    void init(int _n){ndn=_n; edn=0; MST(last,-1);}
+    void adde(int _u, int _v, int _w)
+    {
+        u[edn]=_u; v[edn]=_v; w[edn]=_w;
+        nxt[edn]=last[_u];
+        last[_u] = edn++;
+    }
+};
+
+int N;
+Graph G;
+int dp[maxn][4], pos[maxn][4], dp2[maxn][3], pos2[maxn][3], res[maxn];
+LL ans;
+
+void add(int,int,int);
+void add2(int,int,int);
+int dfs0(int,int);
+int dfs1(int,int,int,int);
+
+int main()
+{
+    #ifdef LOCAL
+    freopen("in.txt", "r", stdin);
+//  freopen("out.txt", "w", stdout);
+    #endif
+
+    int T;
+    scanf("%d", &T);
+    for(int ck=1; ck<=T; ck++)
+    {
+        scanf("%d", &N);
+        G.init(N);
+        for(int i=1, u, v, w; i<N; i++)
+        {
+            scanf("%d%d%d", &u, &v, &w);
+            G.adde(u,v,w); G.adde(v,u,w);
+        }
+        ans = 0;
+        dfs0(1,0);
+        dfs1(1,0,0,0);
+        printf("%lld\n", ans);
+    }
+    return 0;
+}
+
+void add(int u, int v, int val)
+{
+    dp[u][3] = val; pos[u][3] = v;
+    for(int i=2; i>=0; i--) if(dp[u][i] < dp[u][i+1])
+    {
+        swap(dp[u][i], dp[u][i+1]);
+        swap(pos[u][i], pos[u][i+1]);
+    }
+}
+
+void add2(int u, int v, int val)
+{
+    dp2[u][2] = val; pos2[u][2] = v;
+    for(int i=1; i>=0; i--) if(dp2[u][i] < dp2[u][i+1])
+    {
+        swap(dp2[u][i], dp2[u][i+1]);
+        swap(pos2[u][i], pos2[u][i+1]);
+    }
+}
+
+int dfs0(int u, int f)
+{
+    MST(dp[u],-1); MST(pos[u],-1); 
+    MST(dp2[u], -1); MST(pos2[u], -1);
+    res[u] = 0;
+    bool leaf=1;
+    for(int e=G.last[u], v; ~e; e=G.nxt[e]) if((v=G.v[e])!=f)
+    {
+        leaf=0;
+        add(u, v, dfs0(v,u)+G.w[e]);
+        add2(u, v, res[v]);
+        res[u] = max(res[u], res[v]);
+    }
+    if(leaf) add(u, u, 0);
+    res[u] = max(res[u], max(dp[u][0], dp[u][0]+dp[u][1]));
+    return dp[u][0];
+}
+
+int dfs1(int u, int f, int one, int two)
+{
+    for(int e=G.last[u], v; ~e; e=G.nxt[e]) if((v=G.v[e])!=f)
+    {
+        int tmax=0, tp=-1, tmax2=0, none, ntwo;
+        for(int i=0; i<3 && ~dp[u][i]; i++)
+        {
+            if(pos[u][i] == v) continue;
+            if(dp[u][i]>tmax) tmax = dp[u][i], tp=i;
+        }
+        none = max(tmax, one);
+        ntwo = max(two, one+tmax);
+        for(int i=0; i<3 && ~dp[u][i]; i++)
+        {
+            if(pos[u][i] == v || i==tp) continue;
+            tmax2 = max(tmax2, dp[u][i]);
+        }
+        ntwo = max(ntwo, tmax + tmax2);
+        if(pos[u][0] == v) ntwo = max(ntwo, dp2[u][1]);
+        else ntwo = max(ntwo, dp2[u][0]);
+        ans += max(ntwo, res[v]);
+        dfs1(v, u, none+G.w[e], ntwo);
+    }
+
+}