单个边的权值修改以及询问路径上的权值之和。
数据量比较大，用vector存图会超时的。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <algorithm> 5 #include <vector> 6 using namespace std; 7 8 void scan(int& x) 9 { 10 x = 0; 11 int ch = ' '; 12 while(ch < '0' || ch > '9') ch = getchar(); 13 while(ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); } 14 } 15 16 int n, Q, s; 17 18 const int maxn = 100000 + 10; 19 int u[maxn], v[maxn], d[maxn]; 20 21 struct Edge 22 { 23 int v, nxt; 24 }; 25 26 int cnt; 27 int head[maxn]; 28 Edge edge[maxn * 2]; 29 30 void AddEdge(int u, int v) 31 { 32 edge[cnt].v = v; 33 edge[cnt].nxt = head[u]; 34 head[u] = cnt++; 35 } 36 37 int tot; 38 int L[maxn]; 39 int fa[maxn]; 40 int sz[maxn]; 41 int son[maxn]; 42 int id[maxn]; 43 int top[maxn]; 44 45 void dfs(int u) 46 { 47 sz[u] = 1; son[u] = 0; 48 for(int i = head[u]; i != -1; i = edge[i].nxt) 49 { 50 int v = edge[i].v; 51 if(v == fa[u]) continue; 52 fa[v] = u; 53 L[v] = L[u] + 1; 54 dfs(v); 55 sz[u] += sz[v]; 56 if(sz[v] > sz[son[u]]) son[u] = v; 57 } 58 } 59 60 void dfs2(int u, int tp) 61 { 62 top[u] = tp; 63 if(son[u]) { id[son[u]] = ++tot; dfs2(son[u], tp); } 64 for(int i = head[u]; i != -1; i = edge[i].nxt) 65 { 66 int v = edge[i].v; 67 if(v == fa[u] || v == son[u]) continue; 68 id[v] = ++tot; 69 dfs2(v, v); 70 } 71 } 72 73 int sum[maxn << 2]; 74 75 void update(int o, int L, int R, int p, int v) 76 { 77 if(L == R) { sum[o] = v; return ; } 78 int M = (L + R) / 2; 79 if(p <= M) update(o<<1, L, M, p, v); 80 else update(o<<1|1, M+1, R, p, v); 81 sum[o] = sum[o<<1] + sum[o<<1|1]; 82 } 83 84 int query(int o, int L, int R, int qL, int qR) 85 { 86 if(qR < L || qL > R) return 0; 87 if(qL <= L && R <= qR) return sum[o]; 88 int ans = 0; 89 int M = (L + R) / 2; 90 ans += query(o<<1, L, M, qL, qR); 91 ans += query(o<<1|1, M+1, R, qL, qR); 92 return ans; 93 } 94 95 int Query(int u, int v) 96 { 97 int ans = 0; 98 int t1 = top[u], t2 = top[v]; 99 while(t1 != t2) 100 { 101 if(L[t1] < L[t2]) { swap(u, v); swap(t1, t2); } 102 ans += query(1, 1, tot, id[t1], id[u]); 103 u = fa[t1]; t1 = top[u]; 104 } 105 if(u == v) return ans; 106 if(L[u] < L[v]) swap(u, v); 107 ans += query(1, 1, tot, id[son[v]], id[u]); 108 return ans; 109 } 110 111 int main() 112 { 113 while(scanf("%d%d%d", &n, &Q, &s) == 3) 114 { 115 memset(head, -1, sizeof(head)); 116 cnt = 0; 117 for(int i = 1; i < n; i++) 118 { 119 scan(u[i]); scan(v[i]); scan(d[i]); 120 AddEdge(u[i], v[i]); 121 AddEdge(v[i], u[i]); 122 } 123 124 L[1] = fa[1] = 0; 125 dfs(1); 126 tot = 0; 127 dfs2(1, 1); 128 129 memset(sum, 0, sizeof(sum)); 130 for(int i = 1; i < n; i++) 131 { 132 if(L[u[i]] < L[v[i]]) swap(u[i], v[i]); 133 update(1, 1, tot, id[u[i]], d[i]); 134 } 135 136 int op, x, y; 137 while(Q--) 138 { 139 scan(op); 140 if(op == 0) 141 { 142 scan(x); 143 printf("%d ", Query(s, x)); 144 s = x; 145 } 146 else 147 { 148 scan(x); scan(y); 149 update(1, 1, tot, id[u[x]], y); 150 } 151 } 152 } 153 154 return 0; 155 }