POJ1364 King 国王差分约束

/*
*State: POJ1364     Accepted    176K    0MS    C++
*题目大意；
*        已知一个序列a[1], a[2], ......, a[n]，给出它的若干子序列以及对该子序列的
*        约束条件，例如a[si], a[si+1], a[si+2], ......, a[si+ni]，且a[si]＋a[si+1]
*        ＋a[si+2]＋......＋a[si+ni] < or > ki。求是否存在满足以上m个要求的数列。是
*        则输出“lamentable kingdom”,否则输出“successful conspiracy”。
*解题思路：
*        s[a] + s[a+1] + …… + s[b] < c 可以转化成前n项和sum[b] - sum[a - 1] < c，
*        为了能用Bellman_Ford,即将< 转化成 <= ，sum[b] - sum[a - 1] <= c - 1。
*        转化为最长路或者最短路来判断是否有解都可以。
*解题感想；
*        注意题目求约束的最大，或者最小时，就要判断此刻要用的是最短路，还是最长路。
*/

Bellman_ford:

#include <iostream>
#include <queue>
#include <map>
#include <string>
#include <cstdio>
#include <cstring>
using namespace std;

const int MAXN = 105;
const int MAXE = 10005;
const int inf = 10000;

typedef struct _node
{
    int u, v, w;
    int next;
}N;
N edge[MAXE];
int head[MAXN], cntEdge;

void init()
{
    cntEdge = 0;
    for(int i = 0; i < MAXN; i++)
        head[i] = -1;
}

void addEdge(int u, int v, int w)
{
    edge[cntEdge].u = u;
    edge[cntEdge].v = v;
    edge[cntEdge].w = w;
    edge[cntEdge].next = head[u];
    head[u] = cntEdge++;
}

int Bellman_ford(int s, int n)
{
    int dis[MAXN];
    for(int i = 0; i <= n; i++)
        dis[i] = inf;

    dis[s] = 0;
    for(int i = 0; i < n-1; i++)
    {
        bool flag = false;
        for(int j = 0; j < cntEdge; j++)
        {
            int u = edge[j].u;
            int v = edge[j].v;
            int w = edge[j].w;
            if(dis[v] > dis[u] + w)
            {
                dis[v] = dis[u] + w;
                flag = true;
            }
        }
        if(!flag)
            break;
    }
    //cout << "-----------------" << endl;
    //for(int i = 0; i <= n; i++)
    //    cout << dis[i] << " ";
    //cout << "-----------------" << endl;
    for(int f = 0; f < cntEdge; f++)
    {
        int u = edge[f].u, v = edge[f].v;
        int w = edge[f].w;
        if(dis[v] > dis[u] + w)
            return -1;
    }
    return 1;
}

int main(void)
{
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
#endif

    int n, m;
    while(scanf("%d", &n), n)
    {
        scanf("%d", &m);
        int u, v, w;
        char op[5];
        init();
        for(int i = 0; i < m; i++)
        {
            scanf("%d %d %s %d", &u, &v, op, &w);
            if(op[0] == 'g')
                addEdge(u + v + 1, u, -w - 1);
            else
                addEdge(u, u + v + 1, w - 1);
        }
        for(int i = 1; i <= n + 1; i++)
            addEdge(0, i, 0);

        int sol = Bellman_ford(0, n + 2);
        if(sol == -1)
            printf("successful conspiracy\n");
        else
            printf("lamentable kingdom\n");
    }
    return 0;
}

spfa:

//spfa
//State: POJ1364    Accepted    192K    0MS    C++    1759B
#include <iostream>
#include <queue>
#include <map>
#include <string>
#include <cstdio>
#include <cstring>
using namespace std;

const int MAXN = 105;
const int MAXE = 10005;
const int inf = 10000;

typedef struct _node
{
    int u, v, w;
    int next;
}N;
N edge[MAXE];
int head[MAXN], cntEdge;

void init()
{
    cntEdge = 0;
    for(int i = 0; i < MAXN; i++)
        head[i] = -1;
}

void addEdge(int u, int v, int w)
{
    edge[cntEdge].u = u;
    edge[cntEdge].v = v;
    edge[cntEdge].w = w;
    edge[cntEdge].next = head[u];
    head[u] = cntEdge++;
}

int spfa(int s, int n)
{
    queue<int> Q;
    int inQ[MAXN] = {0}, in[MAXN] = {0};
    int dis[MAXN];
    for(int i = 0; i <= n; i++)
        dis[i] = inf;

    Q.push(s);
    dis[s] = 0;
    inQ[s] = 1;
    in[s]++;

    while(!Q.empty())
    {
        int pre = Q.front();
        Q.pop();
        inQ[pre] = 0;
        
        for(int f = head[pre]; f != -1; f = edge[f].next)
        {
            int son = edge[f].v, w = edge[f].w;
            if(dis[son] > dis[pre] + w)
            {
                dis[son] = dis[pre] + w;
                if(!inQ[son])
                {
                    inQ[son] = 1;
                    Q.push(son);
                    in[son]++;
                    if(in[son] > n)
                        return -1;
                }
            }
        }
    }
    return 1;
}

int main(void)
{
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
#endif

    int n, m;
    while(scanf("%d", &n), n)
    {
        scanf("%d", &m);
        int u, v, w;
        char op[5];
        init();
        for(int i = 0; i < m; i++)
        {
            scanf("%d %d %s %d", &u, &v, op, &w);
            if(op[0] == 'g')
                addEdge(u + v + 1, u, -w - 1);
            else
                addEdge(u, u + v + 1, w - 1);
        }
        for(int i = 1; i <= n + 1; i++)
            addEdge(0, i, 0);

        int sol = spfa(0, n + 2);
        if(sol == -1)
            printf("successful conspiracy\n");
        else
            printf("lamentable kingdom\n");
    }
    return 0;
}