|poj 1986|LCA|Distance Queries

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poj1986
LCA模板题
#include<cstdio>#include<cstring>#include<algorithm>#include<vector>#define ms(i, j) memset(i, j, sizeof i)using namespace std;const int MAXN = 40000 + 5, logs = 22;struct edge{    int x, y, v;}ed[MAXN*2];int en;int n, m, deep[MAXN], far[MAXN], pre[MAXN][logs+1];vector<int> G[MAXN];void dfs(int x, int p){    pre[x][0] = p;    for (int i=1;i<=logs;i++) pre[x][i] = pre[pre[x][i-1]][i-1];    for (int i=0;i<G[x].size();i++)    {        int v = ed[G[x][i]].y;        if (v!=p)        {            deep[v] = deep[x] + 1;            far[v] = far[x] + ed[G[x][i]].v;            dfs(v, x);        }    }}int lca(int a, int b){    if (deep[a]>deep[b]) swap(a,b);    for (int i=logs;i>=0;i--) if (deep[pre[b][i]]>=deep[a]) b = pre[b][i];    if (a==b) return a;    for (int i=logs;i>=0;i--) if (pre[a][i]!=pre[b][i]) a = pre[a][i], b = pre[b][i];    return pre[a][0];}void addedge(int x, int y, int v){    en++, ed[en].x = x, ed[en].y = y, ed[en].v = v, G[x].push_back(en);     en++, ed[en].x = y, ed[en].y = x, ed[en].v = v, G[y].push_back(en); }void init(){    for (int i=1;i<=n;i++)    {        G[i].clear();        deep[i] = far[i] = 0;        for (int j=0;j<=logs;j++) pre[i][j] = 0;    }    en = 0;    for (int i=1;i<=m;i++)    {        int x, y, v;        char str[20];        scanf("%d%d%d%s", &x, &y ,&v, str);        addedge(x, y, v);    }}void solve(){    dfs(1, 0);    int q;    scanf("%d", &q);    for (int i=1;i<=q;i++)    {        int x, y;        scanf("%d%d", &x, &y);        printf("%d\n", far[x]+far[y]-2*far[lca(x,y)]);    }}int main(){    while (scanf("%d%d", &n, &m)==2)    {        init();        solve();    }    return 0;}
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