naming nit/consistency

Author: lrvideckis

library/dsu/dsu_bipartite.hpp

@@ -5,13 +5,13 @@
 struct dsu_bipartite {
   vi p, is_bi, parity;
   dsu_bipartite(int n): p(n, -1), is_bi(n, 1), parity(n) {}
-  int f(int v) {
-    if (p[v] < 0) return v;
-    int root = f(p[v]);
-    return parity[v] ^= parity[p[v]], p[v] = root;
+  int f(int u) {
+    if (p[u] < 0) return u;
+    int x = f(p[u]);
+    return parity[u] ^= parity[p[u]], p[u] = x;
   }
-  int size(int v) { return -p[f(v)]; }
-  bool is_bipartite(int v) { return is_bi[f(v)]; }
+  int size(int u) { return -p[f(u)]; }
+  bool is_bipartite(int u) { return is_bi[f(u)]; }
   bool join(int u, int v) {
     int x = f(u), y = f(v);
     int new_parity = parity[u] ^ parity[v];

library/dsu/dsu_weighted.hpp

@@ -14,8 +14,8 @@ struct dsu_weighted {
   dsu_weighted(int n): p(n, -1), d(n) {}
   int f(int u) {
     if (p[u] < 0) return u;
-    int root = f(p[u]);
-    return d[u] += d[p[u]], p[u] = root;
+    int x = f(p[u]);
+    return d[u] += d[p[u]], p[u] = x;
   }
   int size(int u) { return -p[f(u)]; }
   ll diff(int u, int v) {

library/dsu/kruskal_tree.hpp

@@ -7,7 +7,7 @@ struct kr_tree {
   vi p;
   vector<vi> adj;
   kr_tree(int n): id(n), p(2 * n, -1), adj(2 * n) {}
-  int f(int v) { return p[v] < 0 ? v : p[v] = f(p[v]); }
+  int f(int u) { return p[u] < 0 ? u : p[u] = f(p[u]); }
   bool join(int u, int v) {
     if ((u = f(u)) == (v = f(v))) return 0;
     return adj[p[u] = p[v] = id++] = {u, v}, 1;

library/dsu/line_tree.hpp

@@ -22,8 +22,8 @@ struct line_tree {
   line_tree(int n): p(n, -1), last(n), edge(n, {-1, -1}) {
     iota(all(last), 0);
   }
-  int size(int v) { return -p[f(v)]; }
-  int f(int v) { return p[v] < 0 ? v : p[v] = f(p[v]); }
+  int size(int u) { return -p[f(u)]; }
+  int f(int u) { return p[u] < 0 ? u : p[u] = f(p[u]); }
   bool join(int u, int v) {
     u = f(u), v = f(v), id++;
     if (u == v) return 0;