code example

Author: sslotin

segtree_dynamic.cpp

@@ -0,0 +1,30 @@
+struct segtree{
+    int lb, rb;
+    int sum = 0;
+    segtree *l = 0, *r = 0;
+    segtree (int _lb, int _rb) {
+        lb = _lb, rb = _rb;
+    }
+    void extend () {
+        int t = (lb + rb) / 2;
+        if (!l) {
+            l = new segtree(lb, t);
+            r = new segtree(t+1, rb);
+        }
+    }
+    void add (int k, int x) {
+        sum += x;
+        if (lb != rb) {
+            extend();
+            int t = (lb + rb) / 2;
+            if (k <= t) l->add(k, x);
+            else r->add(k, x);
+        }
+    }
+    int get_sum(int lq, int rq){
+        if (lb >= lq && rb <= rq) return sum;
+        if (lb > rq || rb < lq) return 0;
+        extend();
+        return l->get_sum(lq, rq) + r->get_sum(lq, rq);
+    }
+};