new file: 22.cpp

22.cpp

@@ -0,0 +1,40 @@
+// 107
+#include <bits/stdc++.h>
+using namespace std;
+int n;
+int a[500005], tmp[500005];
+long long ms(int l, int r)
+{
+    if (l == r)
+        return 0;
+    int mid = l + r >> 1;
+    long long ans = 0;
+    ans = ms(l, mid) + ms(mid + 1, r);
+    int i = l, j = mid + 1, tot = l;
+    while (i <= mid && j <= r)
+    {
+        if (a[i] > a[j])
+            tmp[tot++] = a[j++], ans+=j-tot;
+        else
+            tmp[tot++] = a[i++];
+    }
+    while (i <= mid)
+        tmp[tot++] = a[i++];
+    while (j <= r)
+        tmp[tot++] = a[j++];
+    for (int i = l; i <= r; ++i)
+        a[i] = tmp[i];
+    return ans;
+}
+int main()
+{
+    scanf("%d", &n);
+    while (n != 0)
+    {
+        for (int i = 1; i <= n; ++i)
+            scanf("%d", &a[i]);
+        printf("%lld\n", ms(1, n));
+        scanf("%d", &n);
+    }
+    return 0;
+}