#include <bits/stdc++.h>
#define pii pair<int, int>
#define x first
#define y second
using namespace std;
const int N = 2e5+5;
int n, m;
int x[N], y[N];
int s[N], t[N];
int za[N], zb[N];
bitset<4> state[N];
bitset<N> check;
int idx;
map<pii, int> Mp;
int par[N<<1];
int find(int u) { return par[u] = par[u] == u ? u : find(par[u]); }
void merge(int a, int b, int c, int d) {
int u = Mp[pii(a, b)], v = Mp[pii(c, d)];
par[find(u)] = find(v);
}
int main() {
iota(par, par+(N<<1), 0);
scanf("%d", &n);
int mnx = 1e9, st;
for(int i = 0; i < n; ++i) {
scanf("%d %d", x+i, y+i);
Mp[pii(x[i], y[i])] = ++idx;
Mp[pii(x[i]+1, y[i])] = ++idx;
Mp[pii(x[i], y[i]+1)] = ++idx;
Mp[pii(x[i]+1, y[i]+1)] = ++idx;
if(y[i] < mnx) mnx = y[i], st = i;
}
scanf("%d", &m);
for(int i = 0; i < m; ++i) {
scanf("%d %d", s+i, t+i), s[i]--, t[i]--;
if(x[s[i]] > x[t[i]]) swap(s[i], t[i]);
if(y[s[i]] > y[t[i]]) swap(s[i], t[i]);
if(x[s[i]] != x[t[i]]) {
state[s[i]][1] = state[t[i]][3] = true;
merge(x[s[i]]+1, y[s[i]], x[t[i]], y[t[i]]);
merge(x[s[i]]+1, y[s[i]]+1, x[t[i]], y[t[i]]+1);
} else {
state[s[i]][0] = state[t[i]][2] = true;
merge(x[s[i]], y[s[i]]+1, x[t[i]], y[t[i]]);
merge(x[s[i]]+1, y[s[i]]+1, x[t[i]]+1, y[t[i]]);
}
}
for(int i = 0; i < n; ++i) {
if(!state[i][0]) merge(x[i], y[i]+1, x[i]+1, y[i]+1);
if(!state[i][1]) merge(x[i]+1, y[i], x[i]+1, y[i]+1);
if(!state[i][2]) merge(x[i], y[i], x[i]+1, y[i]);
if(!state[i][3]) merge(x[i], y[i], x[i], y[i]+1);
}
for(int i = 0; i < m; ++i) {
int a, b;
if(x[s[i]] != x[t[i]])
a = find(Mp[pii(x[t[i]], y[s[i]])]), b = find(Mp[pii(x[t[i]], y[s[i]]+1)]);
else
a = find(Mp[pii(x[t[i]], y[t[i]])]), b = find(Mp[pii(x[t[i]]+1, y[t[i]])]);
za[i] = a, zb[i] = b;
}
int start = find(Mp[pii(x[st], y[st])]);
lv[start] = 1;
Mp.clear();
queue<int> Q; Q.emplace(start);
vector<int> lv(N<<1);
vector<vector<int> > g(N<<1);
for(int i = 0; i < m; ++i) {
g[za[i]].emplace_back(i), g[zb[i]].emplace_back(i);
}
int ans = 0;
while(!Q.empty()) {
int u = Q.front(); Q.pop();
for(int x : g[u]) {
int v = za[x] ^ zb[x] ^ u;
if(lv[v] == 0) lv[v] = lv[u] + 1, Q.emplace(v);
if(lv[v] != lv[u] + 1 && lv[u] != lv[v] + 1) ans++, check[x] = true;
}
}
printf("%d\n", ans >> 1);
for(int i = 0; i < m; ++i) if(check[i]) printf("%d\n", i+1);
}
Compilation message
flood.cpp: In function 'int main()':
flood.cpp:70:5: error: 'lv' was not declared in this scope
lv[start] = 1;
^~
flood.cpp:30:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~
flood.cpp:33:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d", x+i, y+i);
~~~~~^~~~~~~~~~~~~~~~~~~
flood.cpp:40:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &m);
~~~~~^~~~~~~~~~
flood.cpp:42:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d", s+i, t+i), s[i]--, t[i]--;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
