判断是否存在负环

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#include <cstdio>

#include <cstdlib>

#include <cmath>

#include <map>

#include <set>

#include <queue>

#include <stack>

#include <vector>

#include <sstream>

#include <string>

#include <cstring>

#include <algorithm>

#include <iostream>

#define maxn 100010

#define INF 0x7fffffff

#define inf 100000000

#define MOD 1000000007

#define ULL unsigned long long

#define LL long long

using
namespace std;

struct
edge

{

    int
s, v, w;

}p[6100];

int
n, m, w, d[510], num_p;

void
addedge(int
a, int
b, int
c) {

    p[num_p].s = a;

    p[num_p].v = b;

    p[num_p].w = c;

    ++ num_p;

}

bool
bellom_form() {

    for(int
i = 1; i <= n; ++ i) {

        d[i] = inf;

    }

    d[1] = 0;

    for(int
i = 0; i < n-1; ++ i) {

        for(int
j = 0; j < num_p; ++ j) {

            if(d[p[j].v] > d[p[j].s]+p[j].w) {

                d[p[j].v] = d[p[j].s]+p[j].w;

            }

        }

    }

    for(int
i = 0; i < num_p; ++ i) {

        if(d[p[i].v] > d[p[i].s]+p[i].w) {

            return
true;

        }

    }

    return
false;

}

int
main()

{

    int
t;

    scanf("%d", &t);

    while(t --) {

        scanf("%d%d%d", &n, &m, &w);

        num_p = 0;

        for(int
i = 0; i < m; ++ i) {

            int
a, b, c;

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

            addedge(a, b, c);

            addedge(b, a, c);

        }

        for(int
i = 0; i < w; ++ i) {

            int
a, b, c;

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

            addedge(a, b, -c);

        }

        if(bellom_form()) puts("YES");

        else
puts("NO");

    }

    return
0;

}