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Shiroha白羽的博客

Golang 踩坑 —— interface 为参数的时候传 nil 指针 Codeforces Round 925 (Div. 3) Codeforces Round 924 (Div. 2) Codeforces Round 923 (Div. 3) Codeforces Round 922 (Div. 2) Codeforces Round 921 (Div. 2) Educational Codeforces Round 161 (Rated for Div. 2) Codeforces Round 920 (Div. 3) Codeforces Round 919 (Div. 2) Hello 2024 Good Bye 2023 Codeforces Round 918 (Div. 4) 个人备份的常用 macOS 清理命令 Codeforces Round 917 (Div. 2) Pinely Round 3 (Div. 1 + Div. 2) Educational Codeforces Round 160 (Rated for Div. 2) Codeforces Round 915 (Div. 2) Codeforces Round 914 (Div. 2) Codeforces Round 913 (Div. 3) Educational Codeforces Round 159 (Rated for Div. 2) Codeforces Round 912 (Div. 2) Codeforces Round 911 (Div. 2) CodeTON Round 7 (Div. 1 + Div. 2, Rated, Prizes!) Educational Codeforces Round 158 (Rated for Div. 2) Codeforces Round 910 (Div. 2) Codeforces Round 909 (Div. 3) Codeforces Round 908 (Div. 2) Educational Codeforces Round 157 (Rated for Div. 2) C++自定义的字面量 Codeforces Round 907 (Div. 2)
【HDU5934】Bomb——有向图强连通分量+重建图
Shiroha · 2019-10-13 · via Shiroha白羽的博客

二维平面上有 n 个爆炸桶,$i-th$爆炸桶位置为 $(x_i, y_i)$ 爆炸范围为 $r_i$ ,且需要 $c_i$ 的价格引爆,求把所有桶引爆所需的钱。

通过求有向图的强连通分量,求出所有爆炸块(满足引爆一个块内的任意一个爆炸桶就可以摧毁这个块内的爆炸桶),然后把所有爆炸块视为一个爆炸桶,价值为爆炸块内的价值最小值,然后重建有向图,将新建的有向图所有入度为 0 的点的价值相加,就是答案。

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#include <bits/stdc++.h>

using namespace std;

const int MAXN = 1100; // 点数
const int MAXM = 1000100; // 边数
struct Edge {
int to, next;
} edge[MAXM]; // 只有这里写的是 MAXM

int head[MAXN], tot;
int Low[MAXN], DFN[MAXN], Stack[MAXN], Belong[MAXN]; //Belong 数组的值是 1 ~ scc
int Index, top;
int scc; // 强连通分量的个数
bool Instack[MAXN];
int num[MAXN]; // 各个强连通分量包含点的个数,数组编号 1 ~ scc
// num 数组不一定需要,结合实际情况

void addedge(int u, int v) {
edge[tot].to = v;
edge[tot].next = head[u];
head[u] = tot++;
}

void Tarjan(int u) {
int v;
Low[u] = DFN[u] = ++Index;
Stack[top++] = u;
Instack[u] = true;
for (int i = head[u]; i != -1; i = edge[i].next) {
v = edge[i].to;
if (!DFN[v]) {
Tarjan(v);
if (Low[u] > Low[v])
Low[u] = Low[v];
} else if (Instack[v] && Low[u] > DFN[v])
Low[u] = DFN[v];
}
if (Low[u] == DFN[u]) {
scc++;
do {
v = Stack[--top];
Instack[v] = false;
Belong[v] = scc;
num[scc]++;
} while (v != u);
}
}

void solve(int N) {
memset(DFN, 0, sizeof(DFN));
memset(Instack, false, sizeof(Instack));
memset(num, 0, sizeof(num));
Index = scc = top = 0;
for (int i = 1; i <= N; i++)
if (!DFN[i])
Tarjan(i);
}

void init() {
tot = 0;
memset(head, -1, sizeof(head));
}

struct node {
int x, y, r, c;

bool in_boom(const node &other) const {
return hypot(abs(x - other.x), abs(y - other.y)) <= r;
}
};

node nodeList[1100];
int n;

void init_graph1() {
init();
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
if (i == j) continue;
if (nodeList[i].in_boom(nodeList[j]))
addedge(i, j);
}
}
}

struct Graph {
struct Node {
int deg;
int value;
};
Node node[MAXN];

void init() {
for (int i = 0; i < n + 5; ++i) {
node[i].deg = 0;
node[i].value = INT_MAX;
}
}

void add_edge(int from, int to) {
if (from != to)
node[to].deg++;
}
};

Graph graph;
int ans;

void tp_init() {
graph.init();
for (int i = 1; i <= n; ++i) {
graph.node[Belong[i]].value = min(graph.node[Belong[i]].value, nodeList[i].c);
for (int j = 1; j <= n; ++j) {
if (i == j) continue;
if (nodeList[i].in_boom(nodeList[j]))
graph.add_edge(Belong[i], Belong[j]);
}
}
}

void tp() {
ans = 0;
tp_init();

for (int i = 1; i <= scc; ++i) {
if (graph.node[i].deg == 0) {
ans += graph.node[i].value;
}
}
}

void solve() {
int t;
cin >> t;
for (int ts = 0; ts < t; ++ts) {
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> nodeList[i].x >> nodeList[i].y >> nodeList[i].r >> nodeList[i].c;
}
init_graph1();
solve(n);
tp();
cout << "Case #" << ts + 1 << ": " << ans << endl;
}
}

int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
#ifdef ACM_LOCAL
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
long long test_index_for_debug = 1;
char acm_local_for_debug;
while (cin >> acm_local_for_debug) {
cin.putback(acm_local_for_debug);
if (test_index_for_debug > 20) {
throw runtime_error("Check the stdin!!!");
}
auto start_clock_for_debug = clock();
solve();
auto end_clock_for_debug = clock();
cout << "Test " << test_index_for_debug << " successful" << endl;
cerr << "Test " << test_index_for_debug++ << " Run Time: "
<< double(end_clock_for_debug - start_clock_for_debug) / CLOCKS_PER_SEC << "s" << endl;
cout << "--------------------------------------------------" << endl;
}
#else
solve();
#endif
return 0;
}