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42 lines
1004 B
C++
42 lines
1004 B
C++
#define _CRT_SECURE_NO_WARNINGS
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#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
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#include <algorithm>
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#include <cstdio>
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#include <cstring>
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using namespace std;
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#define lowbit(x) ((x) & -(x))
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const int N = 500005;
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int sum[N];
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int query(int x)
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{
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int ans = 0;
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for (; x; x -= lowbit(x)) ans += sum[x];
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return ans;
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}
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void update(int x, int y)
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{
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for (; x <= N; x += lowbit(x)) sum[x] += y;
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}
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struct abcd
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{
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int val, pos;
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bool operator<(const abcd &rhs) const { return val < rhs.val; }
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} nodes[N];
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int main()
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{
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int n;
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while (~scanf("%d", &n) && n)
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{
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memset(sum, 0, sizeof(sum));
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for (int i = 1; i <= n; i++) scanf("%d", &nodes[i].val), nodes[i].pos = i;
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std::sort(nodes + 1, nodes + n + 1);
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long long ans = 0;
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for (int i = 1; i <= n; i++)
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{
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update(nodes[i].pos, 1);
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ans += i - query(nodes[i].pos);
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}
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printf("%lld\n", ans);
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}
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return 0;
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} |