[Original blog] poj 2425 a chess game

Question Link
Given a directed acyclic graph (DAG) with some flags on it, the flag can overlap. Two people can take turns and move a flag from one position to another, if the device cannot be moved, enter and ask if the player must win.

This question can regard each flag as a separate game. Then, the SG values of all these flags are the XOR and SG values of these flags, which can be memorized for searching DFS, the SG value can be used for brute force calculation.

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring> //by zrt//problem:using namespace std;typedef long long LL;const int inf(0x3f3f3f3f);const double eps(1e-9);int n;int H[1005],X[1000005],P[1000005],tot;inline void add(int x,int y){    P[++tot]=y;X[tot]=H[x];H[x]=tot;}int sg[1005];int dfs(int x){    if(~sg[x]) return sg[x];    bool nxt[1005];    memset(nxt,0,sizeof nxt);    for(int i=H[x];i;i=X[i]){        nxt[dfs(P[i])]=1;    }    for(int i=0;;i++){        if(!nxt[i]){            return sg[x]=i;        }    }}int main(){    #ifdef LOCAL    freopen("in.txt","r",stdin);    freopen("out.txt","w",stdout);    #endif    while(~scanf("%d",&n)){        memset(H,0,sizeof H);tot=0;        memset(sg,-1,sizeof sg);        for(int i=0,x;i<n;i++){            scanf("%d",&x);            for(int j=0,y;j<x;j++){                scanf("%d",&y);                add(i,y);            }        }        int q;        while(scanf("%d",&q),q){            int SG=0;            for(int i=0,x;i<q;i++){                scanf("%d",&x);                SG^=dfs(x);            }            if(SG) puts("WIN");            else puts("LOSE");        }    }    return 0;}

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[Original blog] poj 2425 a chess game