added segment tree template

segment_tree.cpp

@@ -0,0 +1,80 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class SegmentTree {
+    int v_size, tree_size;
+    vector<int> tree;
+
+    int get(int l, int r, int tl, int tr, int node) {
+        if(l == tl && r == tr)
+            return tree[node];
+
+        int m = (tl + tr) / 2;
+        if(r <= m)
+            return get(l, r, tl, m, 2 * node);
+        else if(l > m)
+            return get(l, r, m + 1, tr, 2 * node + 1);
+        else
+            return max(get(l, m, tl, m, 2 * node), get(m + 1, r, m + 1, tr, 2 * node + 1))
+    }
+
+public:
+    SegmentTree(const vector<int>& v) {
+        tree_size = 1;
+        v_size = v.size();
+        while(tree_size < v.size())
+            tree_size <<= 1;
+        tree_size <<= 1;
+
+        tree = vector<int>(tree_size, INT_MIN);
+        for(int i = 0; i < v.size(); ++i)
+            update(i, v[i]);
+    }
+
+    void update(int idx, int val) {
+        idx += tree_size / 2;
+        tree[idx] = val;
+
+        idx /= 2;
+        while(idx) {
+            tree[idx] = max(tree[2 * idx], tree[2 * idx + 1]);
+            if(tree[idx] > val)
+                break;
+            idx /= 2;
+        }
+    }
+
+    int query(int l, int r) {
+        return get(l + 1, r + 1, 1, v_size, 1);
+    }
+};
+
+int main() {
+    int n;
+    cin >> n;
+
+    vector<int> v(n);
+    for(int& t : v)
+        cin >> t;
+
+    SegmentTree seg(v);
+
+    while(true) {
+        int t;
+        cin >> t;
+
+        if(t == 1) {
+            int l, r;
+            cin >> l >> r;
+            cout << (seg.query(l, r)) << "\n";
+        }
+        else if(t == 2) {
+            int idx, val;
+            cin >> idx >> val;
+            seg.update(idx, val);
+        }
+        else {
+            break;
+        }
+    }
+}