求助，不开O2 100pts，开了O2 全部TLE 代码

#include <bits/stdc++.h>
using namespace std;
template <typename T>
void readin(T &x) {
	x = 0;
	char ch = getchar();
	T fh = 1;
	for (; !isdigit(ch); ch = getchar()) if (ch == '-') fh = -1;
	for (; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + (ch ^ 48);
	x *= fh;
}
template <typename T>
void wt(T x) {
	if (x > 9) wt(x / 10);
	putchar(x % 10 + 48);
}
template <typename T>
void writeln(T x, char ch) {
	wt(x);
	putchar(ch);
}
const int N = 1e5 + 5;
struct info{
	int to, nex, val;
}l[N << 1];
int n, m, siz[N], f[N], hd[N], g[N][20][2], anc[N][20], dep[N];
int G(int x) {
	if (f[x] == x) return x;
	return f[x] = G(f[x]);
}
int mer(int x, int y) {
	x = G(x);
	y = G(y);
	if (siz[x] > siz[y]) swap(x, y);
	f[x] = y;
	siz[y] += siz[x];
}
void dfs(int p) {
	for (int i = 1; i <= 19; i ++) {
		anc[p][i] = anc[anc[p][i - 1]][i - 1];
		g[p][i][0] = max(g[p][i - 1][0], g[anc[p][i - 1]][i - 1][0]);
		if (g[p][i - 1][0] < g[anc[p][i - 1]][i - 1][0]) {
			g[p][i][1] = max(g[p][i - 1][0], g[anc[p][i - 1]][i - 1][1]);
		}
		else if (g[p][i - 1][0] > g[anc[p][i - 1]][i - 1][0]) {
			g[p][i][1] = max(g[p][i - 1][1], g[anc[p][i - 1]][i - 1][0]);
		}
		else g[p][i][1] = max(g[p][i - 1][1], g[anc[p][i - 1]][i - 1][1]);
	}
	int u;
	for (int e = hd[p]; e; e = l[e].nex) {
		u = l[e].to;
		if (u != anc[p][0]) {
			anc[u][0] = p;
			g[u][0][0] = l[e].val;
			g[u][0][1] = -1e9;
			dep[u] = dep[p] + 1;
			dfs(u);
		}
	}
}
pair <int, int> lca(int x, int y) {
	if (dep[x] < dep[y]) swap(x, y);
	int w = 0, v = -1e9;
	for (int i = 19; i >= 0; i --) {
		if (dep[anc[x][i]] >= dep[y]) {
			if (g[x][i][0] > w) {
				v = max(w, g[x][i][1]);
				w = g[x][i][0];
			}
			else if (g[x][i][0] == w) v = max(v, g[x][i][1]);
			else if (g[x][i][0] > v) v = g[x][i][0];
			x = anc[x][i];
		}
	}
	if (x == y) return make_pair(w, v);
	for (int i = 19; i >= 0; i --) {
		if (anc[x][i] != anc[y][i]) {
			if (g[x][i][0] > w) {
				v = max(w, g[x][i][1]);
				w = g[x][i][0];
			}
			else if (g[x][i][0] == w) v = max(v, g[x][i][1]);
			else if (g[x][i][0] > v) v = g[x][i][0];
			x = anc[x][i];
			if (g[y][i][0] > w) {
				v = max(w, g[y][i][1]);
				w = g[y][i][0];
			}
			else if (g[y][i][0] == w) v = max(v, g[y][i][1]);
			else if (g[y][i][0] > v) v = g[y][i][0];
			y = anc[y][i];
		}
	}
	if (g[x][0][0] > w) {
		v = w;
		w = g[x][0][0];
	}
	else if (g[x][0][0] < w && g[x][0][0] > v) {
		v = g[x][0][0];
	}
	if (g[y][0][0] > w) {
		v = w;
		w = g[y][0][0];
	}
	else if (g[y][0][0] < w && g[y][0][0] > v) {
		v = g[y][0][0];
	}
	return make_pair(w, v);
}
struct ques{
	int x, y, z;
}q[N * 3];
bool comp(ques x, ques y) {
	return x.z < y.z;
}
bool vis[N * 3];
int main() {
	readin(n); readin(m);
	for (int i = 1; i <= n; i ++) {
		f[i] = i;
		siz[i] = 1;
	}
	int u, v, w;
	for (int i = 1; i <= m; i ++) {
		readin(u); readin(v); readin(w);
		q[i] = (ques) {u, v, w};
	}
	sort(q + 1, q + m + 1, comp);
	int len = 0;
	long long val = 0;
	for (int i = 1; i <= m; i ++) {
		if (G(q[i].x) != G(q[i].y)) {
			mer(q[i].x, q[i].y);
			len ++;
			l[len] = (info) {q[i].y, hd[q[i].x], q[i].z};
			hd[q[i].x] = len;
			len ++;
			l[len] = (info) {q[i].x, hd[q[i].y], q[i].z};
			hd[q[i].y] = len;
			val += q[i].z;
			vis[i] = true;
		}
	}
	dep[1] = 1;
	dfs(1);
	pair <int, int> di;
	long long ans = 1e18;
	for (int i = 1; i <= m; i ++) {
		if (!vis[i]) {
			di = lca(q[i].x, q[i].y);
			w = q[i].z;
			if (w > di.first) {
				ans = min(ans, val - di.first + w);
			}
			else if (w > di.second) ans = min(ans, val - di.second + w);
		}
	}
	writeln(ans, '\n');
	return 0;
}

提交记录： 开了O2的 不开O2的