zoj 1508 poj 1201 Intervals

差分约束系统。

#include<cstdio>

#include<cstring>

#include<cmath>

#include<vector>

#include<map>

#include<queue>

#include<algorithm>

using namespace std;

const int maxn = 50005;



map<int, int> jz[maxn];

vector<int>ljb[maxn];

int dist[maxn],flag[maxn];

int mm, mx;



void spfa()

{

    int ii;

    queue<int>Q;

    memset(flag, 0, sizeof(flag));

    flag[mx] = 1; 

    for (ii = 0; ii <= mx; ii++) dist[ii] = 999999999;

    dist[mx] = 0; Q.push(mx);

    while (!Q.empty())

    {

        int hh = Q.front(); Q.pop(); flag[hh] = 0;

        for (ii = 0; ii < ljb[hh].size(); ii++)

        {

            if (jz[hh][ljb[hh][ii]] != 999999999)

            {

                if (dist[hh] + jz[hh][ljb[hh][ii]] < dist[ljb[hh][ii]])

                {

                    dist[ljb[hh][ii]] = dist[hh] + jz[hh][ljb[hh][ii]];

                    if (flag[ljb[hh][ii]] == 0)

                    {

                        Q.push(ljb[hh][ii]);

                        flag[ljb[hh][ii]] = 1;                    

                    }

                }

            }

        }

        

    }

}



int main()

{

    int i, n, a, b, c;

    while (~scanf("%d", &n))

    {

        for (i = 0; i <= 50000; i++) jz[i].clear();

        for (i = 0; i <= 50000; i++) ljb[i].clear();

        mx = -999999999, mm = 999999999;

        for (i = 0; i < n; i++)

        {

            scanf("%d%d%d", &a, &b, &c);

            ljb[b].push_back(a - 1);

            jz[b][a - 1] = -c;

            if (a < mm) mm = a;

            if (b > mx) mx = b;

        }

        for (i = 1; i <= mx; i++)

        {

            ljb[i - 1].push_back(i);

            jz[i - 1][i] = 1;

            ljb[i].push_back(i - 1);

            jz[i][i - 1] = 0;

        }    

        spfa();

        printf("%d\n", dist[mx] - dist[mm - 1]);

    }

    return 0;

}