1 #include <cstdio> 2 #include <cstring> 3 #include <iostream> 4 #define N 100001 5  6 int n, m, cnt; 7 int head[N], to[N << 1], val[N << 1], next[N << 1], dis[N]; 8 bool vis[N]; 9 10 inline int read()11 {12     int x = 0, f = 1;13     char ch = getchar();14     for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;15     for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;16     return x * f;17 }18 19 inline void add(int x, int y, int z)20 {21     to[cnt] = y;22     val[cnt] = z;23     next[cnt] = head[x];24     head[x] = cnt++;25 }26 27 inline bool spfa(int u)28 {29     int i, v;30     vis[u] = 1;31     for(i = head[u]; i ^ -1; i = next[i])32     {33         v = to[i];34         if(dis[v] > dis[u] + val[i])35         {36             dis[v] = dis[u] + val[i];37             if(vis[v]) return 0;38             else if(!spfa(v)) return 0;39         }40     }41     vis[u] = 0;42     return 1;43 }44 45 int main()46 {47     int i, j, opt, x, y, z;48     n = read();49     m = read();50     memset(head, -1, sizeof(head));51     for(i = 1; i <= m; i++)52     {53         opt = read();54         x = read();55         y = read();56         if(opt == 3) add(x, y, 0), add(y, x, 0);57         else58         {59             z = read();60             if(opt == 1) add(x, y, -z);61             if(opt == 2) add(y, x, z);62         }63     }64     memset(dis, 127 / 3, sizeof(dis));65     for(i = 1; i <= n; i++) add(0, i, 0);66     dis[0] = 0;67     spfa(0) ? puts("Yes") : puts("No");68     return 0;69 }