71 lines
1.6 KiB
C++
71 lines
1.6 KiB
C++
#include <iostream>
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#include <ranges>
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#include <queue>
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#include <stdio.h>
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using std::cout,std::iostream;
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static const constexpr auto range {std::ranges::views::iota};
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static const constexpr int MOD {80112002}, MAX_TYPES {(int)5e3+5} /*, MAX_REL_SHIPS {(int)5e5+5}*/;
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static int types, rel_ships, a, b, in_degree[MAX_TYPES], out_degree[MAX_TYPES], link_nums[MAX_TYPES], ans;
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static std::queue<int> q;
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static std::vector<int> next[MAX_TYPES];
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class ReadInt{
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char c;
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int w,n;
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public:
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ReadInt &operator>>(int &num){
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c=0,w=1,n=0;
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while(!isdigit(c)){
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if(c=='-')w=-1;
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c = (char)getchar();
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}
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while(isdigit(c)){
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n=n*10+(c-'0');
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c = (char)getchar();
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}
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num = n*w;
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return *this;
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}
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};
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static ReadInt readint;
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#define cin readint
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int main(){
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cin>>types>>rel_ships;
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for([[maybe_unused]] const int _:range(1,rel_ships+1)){
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cin>>a>>b;
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next[a].push_back(b);
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in_degree[b]++;
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out_degree[a]++;
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}
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for(const int i:range(1, types+1)){
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if(in_degree[i]==0){
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q.push(i);
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link_nums[i] = 1;
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}
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}
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while(!q.empty()){
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auto front {q.front()};
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q.pop();
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for(auto i:next[front]){
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link_nums[i] = (link_nums[i] + link_nums[front])%MOD;
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if(--in_degree[i]==0){
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q.push(i);
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}
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}
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}
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for(auto i:range(1,types+1)){
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if(out_degree[i]==0){
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ans = (ans + link_nums[i]) % MOD;
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}
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}
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cout<<ans<<"\n";
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} |