hdu 5299 Circles Game（博弈）

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题目链接：hdu 5299 Circles Game

每个分离的圆都是单独的游戏，Nim值为该圆嵌套中的圆的Nim和，最后加1.

#include <cstdio>#include <cstring>#include <vector>#include <set>#include <algorithm>using namespace std;const int maxn = 20005;typedef long long ll;struct Circle {    int x, y, r;    void input() {        scanf("%d%d%d", &x, &y, &r);    }}C[maxn];int N, Nim[maxn];vector<int> G[maxn];inline bool cmp(const Circle& a, const Circle& b) {    return a.x < b.x;}inline int distance(int a, int b) {    return a * a + b * b;}bool judge(const Circle& a, const Circle& b) {    return (a.r > b.r) && distance(a.x - b.x, a.y - b.y) < a.r * a.r;}int fa[maxn];void init () {    scanf("%d", &N);    memset(Nim, -1, sizeof(Nim));    for (int i = 0; i < N; i++) {        fa[i] = i;        C[i].input();        G[i].clear();    }    sort(C, C + N, cmp);    for (int i = 0; i < N; i++) {       for (int j = i + 1; j < N && C[j].x - C[i].x <= C[i].r; j++) {           if (judge(C[i], C[j])) {               if (fa[j] == j) fa[j] = i;               else {                   if (C[i].r < C[fa[j]].r) fa[j] = i;               }           }       }       for (int j = i - 1; j >= 0 && C[i].x - C[j].x <= C[i].r; j--) {           if (judge(C[i], C[j])) {               if (fa[j] == j) fa[j] = i;               else {                   if (C[i].r < C[fa[j]].r) fa[j] = i;               }           }       }    }    for (int i = 0; i < N; i++) {        if (fa[i] != i)            G[fa[i]].push_back(i);    }}int SG(int u) {    if (Nim[u] != -1)        return Nim[u];    int& ret = Nim[u];    ret = 0;    for (int i = 0; i < G[u].size(); i++)        ret ^= SG(G[u][i]);    ret += 1;    return ret;}int main () {    int cas;    scanf("%d", &cas);    while (cas--) {        init();        int ans = 0;        for (int i = 0; i < N; i++) {            if (fa[i] == i)                ans ^= SG(i);        }        printf("%s\n", ans ? "Alice" : "Bob");    }    return 0;}

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