diff --git a/Luogu/P1903/P1903.cpp b/Luogu/P1903/P1903.cpp
new file mode 100644
index 00000000..fe0a44d1
--- /dev/null
+++ b/Luogu/P1903/P1903.cpp
@@ -0,0 +1,98 @@
+#include <iostream>
+#include <algorithm>
+#include <tuple>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 200005,
+          M = 1e6 + 5;
+
+int n, m, a[N], cnt[M], t, ans[N];
+std::vector<std::pair<int, int>> c;
+std::vector<std::tuple<int, int, int, int>> q;
+
+inline void add(int x, int &res) {
+    if (!cnt[x]++) res++;
+}
+
+inline void del(int x, int &res) {
+    if (!--cnt[x]) res--;
+}
+
+inline void tim(int x, int i, int j, int &res) {
+    if (j <= c[x].first && c[x].first <= i) {
+        del(a[c[x].first], res);
+        add(c[x].second, res);
+    }
+
+    std::swap(a[c[x].first], c[x].second);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    c.push_back(std::make_pair(0, 0));
+
+    for (int i = 1; i <= m; i++) {
+        char op;
+        int x, y;
+        cin >> op >> x >> y;
+
+        if (op == 'Q') {
+            q.push_back(std::make_tuple(i, x, y, c.size() - 1));
+        } else {  // op == 'C'
+            c.push_back(std::make_pair(x, y));
+        }
+    }
+
+    t = 2609;
+    std::sort(q.begin(), q.end(), [&](auto a, auto b) {
+        int p = std::get<1>(a) / t,
+            q = std::get<1>(b) / t;
+        int x = std::get<2>(a) / t,
+            y = std::get<2>(b) / t;
+
+        return p == q
+                 ? x == y
+                     ? std::get<3>(a) < std::get<3>(b)
+                     : x < y
+                 : p < q;
+    });
+
+    int i = 0, j = 1, now = 0, res = 0;
+    for (auto &e : q) {
+        int id, l, r, t2;
+
+        std::tie(id, l, r, t2) = e;
+
+        while (i < r) add(a[++i], res);
+        while (i > r) del(a[i--], res);
+        while (j < l) del(a[j++], res);
+        while (j > l) add(a[--j], res);
+        while (now < t2) tim(++now, i, j, res);
+        while (now > t2) tim(now--, i, j, res);
+
+        ans[id] = res;
+    }
+
+    std::sort(q.begin(), q.end(), [&](auto a, auto b) {
+        return std::get<0>(a) < std::get<0>(b);
+    });
+
+    for (auto &e : q) {
+        cout << ans[std::get<0>(e)] << endl;
+    }
+
+    return 0;
+}