MCHAOS - Chaos Strings

Tác giả: khuc_tuan

Ngôn ngữ: C++

#include <iostream>
#include <iomanip>
#include <fstream>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#include <cstring>
#include <string>
#include <sstream>
#include <algorithm>
#include <functional>
#include <ctime>
#include <cstdio>
#include <cstdarg>

using namespace std;

#define Rep(i,n) for(int i=0;i<(n);++i)
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Ford(i,a,b) for(int i=(a);i>=(b);--i)
#define Fill(a,b) memset( (a), (b), sizeof(a))
#define pb push_back
#define MP make_pair

char a[100010][12], ra[100010][12];
char *c[100010];
int inv[100010], T[100010];
pair<char*,int> b[100010];
int n;

bool cmp(pair<char*,int> p1, pair<char*,int> p2) {
	return strcmp(p1.first, p2.first) < 0;
}

bool cmp2(char * c1, char * c2) {
	return strcmp(c1, c2) < 0;
}

int main() {
	scanf("%d", &n);
	gets(a[0]);
	for(int i=0;i<n;++i) gets(a[i]);
	for(int i=0;i<n;++i) c[i] = a[i];
	sort( c, c + n, cmp2);
	for(int i=0;i<n;++i) {
		for(int j=strlen(c[i])-1, t=0;j>=0;--j, ++t)
			ra[i][t] = c[i][j];
	}
	for(int i=0;i<n;++i) b[i] = MP(ra[i], i);
	sort(b, b + n, cmp);
	for(int i=0;i<n;++i) inv[b[i].second] = i;
	long long res = 0;
	for(int i=0;i<n;++i) {
		int j;
		for(j=inv[i];j<n;j|=j+1) res += T[j];
		for(j=inv[i];j>=0;j&=j+1,--j) ++T[j];
	}
	printf("%lld\n", res);
	return 0;
}

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