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;
}