洛谷 P3275 [SCOI2011]糖果

传送门

同 AcWing 1169 糖果

Version 1 SPFA

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(1e5 + 10);
bool vis[maxn];
int ecnt, head[maxn], cnt[maxn];
ll dis[maxn];

struct edge {
    int to, wt, nxt;
} edges[maxn * 3];

template<typename T = int>
inline const T read()
{
    T 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 << 3) + (x << 1) + ch - '0';
        ch = getchar();
    }
    return x * f;
}

template<typename T>
inline void write(T x, bool ln)
{
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10, false);
    putchar(x % 10 + '0');
    if (ln) putchar(10);
}

void addEdge(int u, int v, int w)
{
    edges[ecnt].to = v;
    edges[ecnt].wt = w;
    edges[ecnt].nxt = head[u];
    head[u] = ecnt++;
}

bool spfa(int n)
{
    memset(dis, -0x3f, sizeof dis);
    dis[0] = 0;
    stack<int> st;
    st.push(0);
    vis[0] = true;
    while (not st.empty()) {
        int u = st.top();
        st.pop();
        vis[u] = false;
        for (int i = head[u]; compl i; i = edges[i].nxt) {
            int v = edges[i].to, w = edges[i].wt;
            if (dis[v] < dis[u] + w) {
                dis[v] = dis[u] + w;
                if (not vis[v]) {
                    vis[v] = true;
                    st.push(v);
                    cnt[v] = cnt[u] + 1;
                    if (cnt[v] >= n + 1) {
                        return false;
                    }
                }
            }
        }
    }
    return true;
}

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("input.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);
    memset(head, -1, sizeof head);
    int n = read(), k = read();
    while (k--) {
        int x = read(), u = read(), v = read();
        if (x == 1) {
            addEdge(v, u, 0);
            addEdge(u, v, 0);
        } else if (x == 2) {
            addEdge(u, v, 1);
        } else if (x == 3) {
            addEdge(v, u, 0);
        } else if (x == 4) {
            addEdge(v, u, 1);
        } else {
            addEdge(u, v, 0);
        }
    }
    for (int i = 1; i <= n; ++i) {
        addEdge(0, i, 1);
    }
    if (spfa(n)) {
        printf("%lld
", accumulate(dis + 1, dis + 1 + n, 0ll));
    } else {
        printf("-1
");
    }
    return 0;
}

Version 2 Tarjan

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(1e5 + 10);
const int maxm(6e5 + 10);
int ecnt, head[maxn], shead[maxn];
int tim, dfn[maxn], low[maxn];
int scnt, scc[maxn], siz[maxn];
int dis[maxn];
bool vis[maxn];
stack<int> st;

struct edge {
    int to, wt, nxt;
} edges[maxm];

template<typename T = int>
inline const T read()
{
    T 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 << 3) + (x << 1) + ch - '0';
        ch = getchar();
    }
    return x * f;
}

template<typename T>
inline void write(T x, bool ln)
{
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10, false);
    putchar(x % 10 + '0');
    if (ln) putchar(10);
}

void addEdge(int u, int v, int w, bool s = false)
{
    edges[ecnt].to = v;
    edges[ecnt].wt = w;
    if (s) {
        edges[ecnt].nxt = shead[u];
        shead[u] = ecnt++;
    } else {
        edges[ecnt].nxt = head[u];
        head[u] = ecnt++;
    }
}

void tarjan(int u)
{
    dfn[u] = low[u] = ++tim;
    st.push(u);
    vis[u] = true;
    for (int i = head[u]; compl i; i = edges[i].nxt) {
        int v = edges[i].to;
        if (not dfn[v]) {
            tarjan(v);
            low[u] = min(low[u], low[v]);
        } else if (vis[v]) {
            low[u] = min(low[u], dfn[v]);
        }
    }
    if (dfn[u] == low[u]) {
        ++scnt;
        int v = -1;
        do {
            v = st.top();
            st.pop();
            vis[v] = false;
            scc[v] = scnt;
            ++siz[scnt];
        } while (v not_eq u);
    }
}

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("input.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);
    memset(head, -1, sizeof head);
    memset(shead, -1, sizeof shead);
    int n = read(), m = read();
    while (m--) {
        int t = read(), u = read(), v = read();
        if (t == 1) {
            addEdge(u, v, 0);
            addEdge(v, u, 0);
        } else if (t == 2) {
            addEdge(u, v, 1);
        } else if (t == 3) {
            addEdge(v, u, 0);
        } else if (t == 4) {
            addEdge(v, u, 1);
        } else {
            addEdge(u, v, 0);
        }
    }
    for (int i = 1; i <= n; ++i) {
        addEdge(0, i, 1);
    }
    tarjan(0);
    bool flag = true;
    for (int u = 0; u <= n; ++u) {
        for (int i = head[u]; compl i; i = edges[i].nxt) {
            int v = edges[i].to, w = edges[i].wt;
            int a = scc[u], b = scc[v];
            if (a not_eq b) {
                addEdge(a, b, w, true);
            } else if (w > 0) {
                flag = false;
                break;
            }
        }
        if (not flag) {
            break;
        }
    }
    if (not flag) {
        write(-1, true);
    } else {
        for (int u = scnt; u; --u) {
            for (int i = shead[u]; compl i; i = edges[i].nxt) {
                int v = edges[i].to, w = edges[i].wt;
                dis[v] = max(dis[v], dis[u] + w);
            }
        }
        ll sum = 0;
        for (int i = 1; i <= scnt; ++i) {
            sum += dis[i] * siz[i];
        }
        write(sum, true);
    }
    return 0;
}