updated some bugs

data-structure/dsu.cpp

@@ -1,6 +1,6 @@
 // code 1
-const int MX = 2e5;
-int dsu[MX+5], sz[MX+5];
+const int N = 2e5;
+int dsu[N+5], sz[N+5];
 // sz[] is initialized by value 1;
 // dsu[] if initialized by dsu[K] = K
 

data-structure/lca.cpp

@@ -1,6 +1,7 @@
-const int N= 1e5+5,LOG= 20;
-int depth[N],up[N][LOG];
+const int N= 1e5+5, LOG= 20;
+int depth[N+5], up[N+5][LOG];
 vector<int> v[N];
+
 void dfs(int pos,int pre)
 {
    for(auto it:v[pos])
@@ -14,7 +15,6 @@ void dfs(int pos,int pre)
       }
       dfs(it,pos);
    }
-   return ;
 }
 int kthancestor(int pos,int k)
 {
@@ -47,3 +47,6 @@ int get_lca(int a, int b)
     return up[a][0];
 }
 
+
+// initialize with ...
+up[root][0] = root;

data-structure/segment-tree.cpp

@@ -50,7 +50,7 @@ void update(int at, int l, int r, int idx, int num)
 int query(int at, int l, int r, int L, int R)
 {
 	// query from l to r.
-	if(R < l || L > r) return 0;
+	if(r < l || R < l || L > r) return 0;
 	if(L <= l && r <= R) return sum[at];
 
 	int mid = (l+r)/2;

geometry/convex-hull.cpp

@@ -18,37 +18,37 @@ bool ccw(pt a, pt b, pt c, bool include_collinear) {
     return o > 0 || (include_collinear && o == 0);
 }
 
-void convex_hull(vector<pt>& a, bool include_collinear = false) {
-    if (a.size() == 1)
+void convex_hull(vector<pt>& ara, bool include_collinear = false) {
+    if (ara.size() == 1)
         return;
 
-    sort(a.begin(), a.end(), [](pt a, pt b) {
+    sort(ara.begin(), ara.end(), [](pt a, pt b) {
         return make_pair(a.x, a.y) < make_pair(b.x, b.y);
     });
-    pt p1 = a[0], p2 = a.back();
+    pt p1 = ara[0], p2 = ara.back();
     vector<pt> up, down;
     up.push_back(p1);
     down.push_back(p1);
-    for (int i = 1; i < (int)a.size(); i++) {
-        if (i == a.size() - 1 || cw(p1, a[i], p2, include_collinear)) {
-            while (up.size() >= 2 && !cw(up[up.size()-2], up[up.size()-1], a[i], include_collinear))
+    for (int i = 1; i < (int)ara.size(); i++) {
+        if (i == ara.size() - 1 || cw(p1, ara[i], p2, include_collinear)) {
+            while (up.size() >= 2 && !cw(up[up.size()-2], up[up.size()-1], ara[i], include_collinear))
                 up.pop_back();
-            up.push_back(a[i]);
+            up.push_back(ara[i]);
         }
-        if (i == a.size() - 1 || ccw(p1, a[i], p2, include_collinear)) {
-            while (down.size() >= 2 && !ccw(down[down.size()-2], down[down.size()-1], a[i], include_collinear))
+        if (i == ara.size() - 1 || ccw(p1, ara[i], p2, include_collinear)) {
+            while (down.size() >= 2 && !ccw(down[down.size()-2], down[down.size()-1], ara[i], include_collinear))
                 down.pop_back();
-            down.push_back(a[i]);
+            down.push_back(ara[i]);
         }
     }
 
-    if (include_collinear && up.size() == a.size()) {
-        reverse(a.begin(), a.end());
+    if (include_collinear && up.size() == ara.size()) {
+        reverse(ara.begin(), ara.end());
         return;
     }
-    a.clear();
+    ara.clear();
     for (int i = 0; i < (int)up.size(); i++)
-        a.push_back(up[i]);
+        ara.push_back(up[i]);
     for (int i = down.size() - 2; i > 0; i--)
-        a.push_back(down[i]);
+        ara.push_back(down[i]);
 }