2429: [HAOI2006]聪明的猴子 (生成树)

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#include<algorithm>#include<iostream>#include<cstdio>using namespace std;inline int read() {    int x = 0, f = 1;    char ch = getchar();    while (ch < '0' || ch > '9') {        if (ch == '-')f = -1;        ch = getchar();    }    while (ch >= '0' && ch <= '9') {        x = x * 10 + ch - '0';        ch = getchar();    }    return x*f;}struct edge {    int x, y, v;} e[500001];int n, m, tot, cnt, mx, ans, fa[1001], a[501], x[1001], y[1001];inline bool cmp(edge a, edge b) {    return a.v < b.v;}inline int find(int x) {    return x == fa[x] ? x : fa[x] = find(fa[x]);}int main() {    m = read();    for (int i = 1; i <= m; i++)        a[i] = read();    n = read();    for (int i = 1; i <= n; i++) {        fa[i] = i;        x[i] = read();        y[i] = read();    }    for (int i = 1; i < n; i++)        for (int j = i + 1; j <= n; j++)            e[++cnt] = (edge){i, j, (x[i] - x[j])*(x[i] - x[j])+(y[i] - y[j])*(y[i] - y[j])};    sort(e + 1, e + cnt + 1, cmp);    for (int i = 1; i <= cnt; i++) {        int p = find(e[i].x), q = find(e[i].y);        if (p != q) {            fa[p] = q;            tot++;            if (tot == n - 1) {                mx = e[i].v;                break;            }        }    }    for (int i = 1; i <= m; i++)        if (a[i] * a[i] >= mx)            ans++;    printf("%d", ans);    return 0;}

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