Submission #31739

#	Time	Username	Problem	Language	Result	Execution time	Memory
31739		top34051	Beads and wires (APIO14_beads)	C++14	0 / 100	6 ms	4992 KiB

beads

#include<bits/stdc++.h>
using namespace std;
#define maxn 200005
#define inf (long long)2e10

int n;
int par[maxn];
long long mx[2], mem[maxn][2];
vector<int> p;
vector<pair<int,long long> > from[maxn];

void dfs(int x) {
    int i,y;
    for(i=0;i<from[x].size();i++) {
        y = from[x][i].first;
        if(y==par[x]) continue;
        par[y] = x;
        dfs(y);
    }
    p.push_back(x);
}

void upd(long long val) {
    for(int i=0;i<2;i++) if(mx[i]<val) swap(mx[i],val);
}

main() {
    int i,x,y,now;
    long long val, sum, temp;
    scanf("%d",&n);
    for(i=0;i<n-1;i++) {
        scanf("%d%d%lld",&x,&y,&val);
        from[x].push_back({y,val});
        from[y].push_back({x,val});
    }
    par[1] = 0;
    dfs(1);
    for(now=0;now<p.size();now++) {
        x = p[now];
        //Prep
        sum = 0;
        mx[0] = mx[1] = -inf;
        for(i=0;i<from[x].size();i++) {
            y = from[x][i].first; val = from[x][i].second;
            temp = max(mem[y][0], mem[y][1] + val);
            if(y!=par[x]) {
                sum += temp;
                upd(mem[y][0] + val - temp);
            }
        }
        //Don't Fix
        mem[x][0] = max(sum, sum + mx[0] + mx[1]);
        //Fix
        mem[x][1] = max(-inf, sum + mx[0]);
//        printf("mem %d : %lld and %lld\n",x,mem[x][0],mem[x][1]);
    }
    printf("%lld",mem[x][0]);
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(int)':
beads.cpp:14:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0;i<from[x].size();i++) {
             ~^~~~~~~~~~~~~~~
beads.cpp: At global scope:
beads.cpp:27:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^
beads.cpp: In function 'int main()':
beads.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(now=0;now<p.size();now++) {
               ~~~^~~~~~~~~
beads.cpp:43:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(i=0;i<from[x].size();i++) {
                 ~^~~~~~~~~~~~~~~
beads.cpp:30:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
beads.cpp:32:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%lld",&x,&y,&val);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43