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
", dist[mx] - dist[mm - 1]);
    }
    return 0;
}