一、題目描述
二、算法分析說明與代碼編寫指導
三、AC 代碼
#include<cstdio>
#include<algorithm>
#pragma warning(disable:4996)
using namespace std;
struct edge { unsigned u, v; int d; };
unsigned n, m, ml, md; edge e[40000]; int d[1001]; bool updated;
inline bool HasNegativeLoop() {
fill(d + 1, d + n + 1, 1 << 30); d[1] = 0;
for (unsigned i = 1; i < n; ++i) {
updated = false;
for (unsigned j = 0; j < m; ++j) {
if (d[e[j].v] > d[e[j].u] + e[j].d) { d[e[j].v] = d[e[j].u] + e[j].d; updated = true; }
}
if (updated == false)return false;
}
for (unsigned j = 0; j < m; ++j) {
if (d[e[j].v] > d[e[j].u] + e[j].d) { d[e[j].v] = d[e[j].u] + e[j].d; return true; }
}
return false;
}
int main() {
scanf("%u%u%u", &n, &ml, &md);
for (unsigned i = 1; i <= ml; ++i) { scanf("%u%u%d", &e[m].u, &e[m].v, &e[m].d); ++m; }
for (unsigned i = 1; i <= md; ++i) { scanf("%u%u%d", &e[m].v, &e[m].u, &e[m].d); e[m].d *= -1; ++m; }
if (HasNegativeLoop() == true)puts("-1");
else if (d[n] == 1 << 30)puts("-2");
else printf("%d\n", d[n]);
return 0;
}