UVALive 6508 Permutation Graphs

Permutation Graphs

Time Limit: 3000ms

Memory Limit: 131072KB

This problem will be judged on UVALive. Original ID: 6508
64-bit integer IO format: %lld      Java class name: Main

 

解题：逆序数

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int maxn = 100010;
int c[maxn],hhash[maxn],n;
void add(int i){
    while(i > 0){
        c[i] += 1;
        i -= i&-i;
    }
}
int sum(int i,int ret = 0){
    while(i < maxn){
        ret += c[i];
        i += i&-i;
    }
    return ret;
}
int main(){
    int kase,tmp;
    scanf("%d",&kase);
    while(kase--){
        scanf("%d",&n);
        for(int i = 1; i <= n; ++i){
            scanf("%d",&tmp);
            hhash[tmp] = i;
        }
        memset(c,0,sizeof c);
        LL ret = 0;
        for(int i = 0; i < n; ++i){
            scanf("%d",&tmp);
            ret += sum(hhash[tmp] + 1);
            add(hhash[tmp]);
        }
        printf("%lld
",ret);
    }
    return 0;
}