Add solution for CodeChef problem BOMBING (gopalgoel19#53)

Problem statement: https://www.codechef.com/problems/BOMBING

codechef/bombing.cpp

@@ -0,0 +1,93 @@
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+#include <iostream>
+#include <set>
+#include <utility>
+#include <vector>
+using namespace std;
+
+#define LSB(i) ((i) & -(i))
+
+struct Command {
+  char c;
+  int x, y;
+};
+
+vector<Command> read_input() {
+  int n, m;
+  scanf("%d%d", &n, &m);
+  vector<Command> cmds(m);
+  for (auto& cmd : cmds) {
+    scanf(" %c%d", &cmd.c, &cmd.x);
+    if (cmd.c != 'B') {
+      scanf("%d", &cmd.y);
+    }
+  }
+  return cmds;
+}
+
+vector<int> compute_indices(const vector<Command>& cmds) {
+  set<int> indices;
+  vector<pair<int, int>> segments;
+  for (auto& cmd : cmds) {
+    if (cmd.c == 'P') {
+      segments.push_back(make_pair(cmd.x, cmd.y));
+      indices.insert(cmd.x);
+      indices.insert(cmd.y + 1);
+    } else if (cmd.c == 'M') {
+      segments[cmd.x - 1].first += cmd.y;
+      segments[cmd.x - 1].second += cmd.y;
+      indices.insert(segments[cmd.x - 1].first);
+      indices.insert(segments[cmd.x - 1].second + 1);
+    } else {
+      indices.insert(cmd.x);
+    }
+  }
+  return vector<int>(indices.begin(), indices.end());
+}
+
+int sum(const vector<int>& fenwick_tree, int i) {
+  int res = 0;
+  while (i > 0) {
+    res += fenwick_tree[i];
+    i -= LSB(i);
+  }
+  return res;
+}
+
+void add(vector<int>& fenwick_tree, int i, int k) {
+  while (i < int(fenwick_tree.size())) {
+    fenwick_tree[i] += k;
+    i += LSB(i);
+  }
+}
+
+int get_index(const vector<int>& indices, int k) {
+  auto it = lower_bound(indices.begin(), indices.end(), k);
+  assert(*it == k);
+  return it - indices.begin();
+}
+
+int main() {
+  auto cmds = read_input();
+  auto indices = compute_indices(cmds);
+  vector<int> fenwick_tree(indices.size() + 1, 0);
+  vector<pair<int, int>> segments;
+  for (auto& cmd : cmds) {
+    if (cmd.c == 'P') {
+      segments.push_back(make_pair(cmd.x, cmd.y));
+      add(fenwick_tree, get_index(indices, cmd.x) + 1, 1);
+      add(fenwick_tree, get_index(indices, cmd.y + 1) + 1, -1);
+    } else if (cmd.c == 'M') {
+      add(fenwick_tree, get_index(indices, segments[cmd.x - 1].first) + 1, -1);
+      add(fenwick_tree, get_index(indices, segments[cmd.x - 1].second + 1) + 1, 1);
+      segments[cmd.x - 1].first += cmd.y;
+      segments[cmd.x - 1].second += cmd.y;
+      add(fenwick_tree, get_index(indices, segments[cmd.x - 1].first) + 1, 1);
+      add(fenwick_tree, get_index(indices, segments[cmd.x - 1].second + 1) + 1, -1);
+    } else {
+      printf("%d\n", sum(fenwick_tree, get_index(indices, cmd.x) + 1));
+    }
+  }
+}