delete pics to save space

7.2299.cpp

@@ -0,0 +1,33 @@
+#include<cstdio>
+#include<cstring>
+typedef long long LL;
+const int maxn=500005;
+int n,a[maxn],b[maxn]; LL tot;
+void GB(int *a,int *b,int len)
+{
+	if(len<=1) return;
+	int M=len/2,p1=0,p2=M,p=0;
+	GB(a,b,M); GB(a+M,b+M,len-M);
+	while(p1<M&&p2<len)
+	{
+		if(a[p1]<=a[p2]) b[p++]=a[p1++];
+		else { b[p++]=a[p2++]; tot+=M-p1; }
+	}
+	while(p1<M) b[p++]=a[p1++];
+	while(p2<len) b[p++]=a[p2++];
+	memcpy(a,b,len<<2);
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d",&n)==1&&n)
+	{
+		for(int i=0;i<n;i++) scanf("%d",&a[i]);
+		tot=0;
+		GB(a,b,n);
+		printf("%lld\n",tot);
+	}
+	return 0;
+}