Submission #217669

#	Time	Username	Problem	Language	Result	Execution time	Memory
217669		mhy908	Islands (IOI08_islands)	C++14	Compilation error	0 ms	0 KiB

islands

#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define sortvec(x) sort(all(x))
#define compress(x) x.erase(unique(all(x)), x.end())
using namespace std;
typedef long long LL;
typedef pair<int, int> pii;
typedef pair<LL, LL> pll;
typedef pair<int, LL> pil;
typedef pair<LL, int> pli;
const LL llinf=1987654321987654321;
const int inf=2000000000;
int n;
vector<pil> link[1000010];

bool ch[1000010];
LL ret, ans;
vector<int> cyc;
vector<LL> sum;
LL get_cyc(int num, int par){
    if(ch[num]){
        cyc.pb(num);
        sum.pb(0);
        return 0;
    }
    LL retnum=-llinf;
    ch[num]=true;
    int t=0;
    for(auto i:link[num]){
        if(i.F==par&&!t){
            t++;
            continue;
        }
        LL temp=get_cyc(i.F, num)+i.S;
        if(temp>=0){
            cyc.pb(num);
            sum.pb(temp);
            if(cyc[0]!=num)retnum=temp;
        }
    }
    return retnum;
}

LL get_maxd(int num, int par1, int par2){
    LL ret2=0;
    for(auto i:link[num]){
        if(i.F==par1||i.F==par2)continue;
        LL temp=get_maxd(i.F, num, num)+i.S;
        ret=max(ret, ret2+temp);
        ret2=max(ret2, temp);
    }
    return ret2;
}

LL solve(int num){
    cyc.clear(); sum.clear();
    ret=0;
    get_cyc(num, 0);
    for(auto i:cyc)ch2[i]=true;
    LL max1=llinf, max2=-llinf, dia=sum.back();
    cyc.pop_back();
    sum.pop_back();
    int sz=cyc.size();
    for(int i=0; i<sz; i++){
        LL tmp=get_maxd(cyc[i], cyc[(i+sz-1)%sz], cyc[(i+1)%sz]);
        ret=max(ret, sum[i]+tmp-max1);
        ret=max(ret, dia-sum[i]+tmp+max2);
        max2=max(max2, sum[i]+tmp);
        max1=min(max1, sum[i]-tmp);
    }
    return ret;
}

int main(){
    scanf("%d", &n);
    for(int i=1; i<=n; i++){
        int a; LL b;
        scanf("%d %lld", &a, &b);
        link[i].pb(mp(a, b));
        link[a].pb(mp(i, b));
    }
    for(int i=1; i<=n; i++){
        if(ch[i])continue;
        ans+=solve(i);
    }
    printf("%lld", ans);
}

Compilation message (stderr)

islands.cpp: In function 'LL solve(int)':
islands.cpp:63:20: error: 'ch2' was not declared in this scope
     for(auto i:cyc)ch2[i]=true;
                    ^~~
islands.cpp:63:20: note: suggested alternative: 'ch'
     for(auto i:cyc)ch2[i]=true;
                    ^~~
                    ch
islands.cpp: In function 'int main()':
islands.cpp:79:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
islands.cpp:82:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %lld", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~~~~