#3631. Swap

http://www.nfls.com.cn:20035/submission/591497

NFLSOJ/0/3631/3631.cpp

@@ -0,0 +1,46 @@
+// #include <iostream>
+#include <algorithm>
+#include <fstream>
+#include <utility>
+#include <vector>
+
+// using std::cin;
+// using std::cout;
+std::ifstream cin("swap.in");
+std::ofstream cout("swap.out");
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, a[N], p[N];
+std::vector<std::pair<int, int>> ans;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+
+        p[a[i]] = i;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (a[i] != i) {
+            int x = i, y = p[i];
+            ans.emplace_back(p[x], p[y]);
+            std::swap(a[x], a[y]);
+            p[a[x]] = x, p[a[y]] = y;
+        }
+    }
+
+    cout << ans.size() << endl;
+
+    for (auto e : ans) {
+        cout << e.first << ' ' << e.second << endl;
+    }
+
+    return 0;
+}