POJ - 1511 题目链接
一个非常玄学的操作
同样的代码,我用c++就直接wa,用G++成功ac,这是为什么???
说题目思路吧
这显然是一题建立反向边的题,n稍微大一点到了1e6的级别,所以朴素版的Dijkstra是肯定过不了的,考虑用堆优化的1e6log(1e6)稳过,这道题目限时8000ms。
之前也有一道建立方向边的题目,懒得打代码,直接抄下来,改了一改直接用了
还有一个要注意的就是这道题目要用long long,1e6 * 1e6嘛,不在int的范围内。
代码
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> PII;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int N1 = 1e6 + 10, N2 = 1e6 + 10;
ll head1[N1], to1[N2], nex1[N2], value1[N2], visit1[N1], dis1[N1], cnt1 = 1;
ll head2[N1], to2[N2], nex2[N2], value2[N2], visit2[N1], dis2[N2], cnt2 = 1;
int n, m, s;
struct cmp {
bool operator () (const PII & a, const PII & b) const {
return a.second > b.second;
}
};
void add1(ll x, ll y, ll w) {
to1[cnt1] = y;
value1[cnt1] = w;
nex1[cnt1] = head1[x];
head1[x] = cnt1++;
}
void add2(ll x, ll y, ll w) {
to2[cnt2] = y;
value2[cnt2] = w;
nex2[cnt2] = head2[x];
head2[x] = cnt2++;
}
void Dijkstra1() {
priority_queue<PII, vector<PII>, cmp> q;
for(int i = 1; i <= n; i++) dis1[i] = INF;
dis1[1] = 0;
q.push(make_pair(1, 0));
while(!q.empty()) {
ll temp = q.top().first;
q.pop();
if(visit1[temp]) continue;
visit1[temp] = 1;
for(ll i = head1[temp]; i; i = nex1[i])
if(dis1[to1[i]] > dis1[temp] + value1[i]) {
dis1[to1[i]] = dis1[temp] + value1[i];
q.push(make_pair(to1[i], dis1[to1[i]]));
}
}
}
void Dijkstra2() {
priority_queue<PII, vector<PII>, cmp> q;
for(int i = 1; i <= n; i++) dis2[i] = INF;
dis2[1] = 0;
q.push(make_pair(1, 0));
while(!q.empty()) {
ll temp = q.top().first;
q.pop();
if(visit2[temp]) continue;
visit2[temp] = 1;
for(ll i = head2[temp]; i; i = nex2[i])
if(dis2[to2[i]] > dis2[temp] + value2[i]) {
dis2[to2[i]] = dis2[temp] + value2[i];
q.push(make_pair(to2[i], dis2[to2[i]]));
}
}
}
int main() {
// freopen("in.txt", "r", stdin);
ll x, y, w, t;
scanf("%lld", &t);
while(t--) {
scanf("%lld %lld", &n, &m);
memset(visit1, 0, sizeof visit1);
memset(visit2, 0, sizeof visit2);
memset(head1, 0, sizeof head1);
memset(head2, 0, sizeof head2);
cnt1 = cnt2 = 1;
for(int i = 0; i < m; i++) {
scanf("%lld %lld %lld", &x, &y, &w);
add1(x, y, w);
add2(y, x, w);
}
Dijkstra1();
Dijkstra2();
ll ans = 0;
for(int i = 1; i <= n; i++)
ans += dis1[i] + dis2[i];
printf("%lld\n", ans);
}
return 0;
}