nyoj- 117 求逆序数 && hdu-sort it----> 树状数组

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nyoj-117（离散化）

 #include<stdio.h>#include<string.h>#include<algorithm>using namespace std;long long a[1000009];int n;struct ni{    int v,w;}b[1000009];int cmp(ni q,ni p){    if(q.v!=p.v) return q.v<p.v;    return q.w<p.w;}int lowbit(int x){    return x&(-x);}int sum(int pos){    int res=0;    while(pos>0)    {        res+=a[pos];        pos-=lowbit(pos);    }    return res;}void plus(int pos){    while(pos<=n)    {        a[pos]++;        pos+=lowbit(pos);    }}int main(){    int m,i;    scanf("%d",&m);    while(m--)    {        memset(a,0,sizeof(a));        scanf("%d",&n);        for(i=1;i<=n;i++)        {            scanf("%d",&b[i].v);            b[i].w=i;        }        sort(b+1,b+n+1,cmp);        long long k=0;        for(i=1;i<=n;i++)        {            plus(b[i].w);            k+=i-sum(b[i].w);        }        printf("%lld\n",k);    }}

hdu-sort it

#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;int a[1005];int n;int lowbit(int x){    return x&(-x);}void add(int pos,int num){    while(pos <= n)    {        a[pos] += num;        pos += lowbit(pos);    }}int Get_sum(int pos){    int res = 0;    while(pos > 0)    {        res += a[pos];        pos -= lowbit(pos);    }    return res;}int main(){    int x;    while(~scanf("%d",&n))    {        memset(a,0,sizeof(a));        int sum = 0;        for(int i = 1; i <= n; i++)        {            scanf("%d",&x);            add(x,1);            sum += i - Get_sum(x);        }        printf("%d\n",sum);    }}

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