树状数组 POJ 2481 Cows

题目传送门

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;

 const int MAX_N =  + ;
 int cnt[MAX_N];
 int ans[MAX_N];
 int maxn = -;
 struct node
 {
     int s, e;
     int id;
 }cow[MAX_N];

 inline int read(void)
 {
     int x = , f = ;    char ch = getchar ();
     while (ch < '' || ch > '')    {if (ch == '-')    f = -;    ch = getchar ();}
     while (ch >= '' && ch <= '')    {x = x *  + ch - '';    ch = getchar ();}
     return x * f;
 }

 inline void print(int x)
 {
     if (x < )    {putchar ('-');    x = -x;}
     if (x > )    print (x / );
     putchar (x %  + '');
 }

 bool cmp(node x, node y)        //先对e从大到小排序
 {
     if (x.e == y.e)
         return x.s < y.s;        //如果如果相等，再按s从小到大排序
     else
         return x.e > y.e;
 }

 int lowbit(int t)        //求 2^t
 {
     //return t & (t ^ (t - 1));
     return t & (-t);
 }

 void plus(int x)
 {
     while (x <= maxn)
     {
         ans[x]++;                //记录强壮的牛数
         x += lowbit (x);
     }
 }

 int sum(int x)                    //统计前x项强壮的牛数
 {
     int sum = ;
     while (x > )
     {
         sum += ans[x];
         x -= lowbit(x);
     }
     return sum;
 }

 int main(void)        //POJ 2481 Cows
 {
     //freopen ("inH.txt", "r", stdin);
     int n;

     while (scanf ("%d", &n) && n)
     {
         for (int i=; i<=n; ++i)
         {
             cow[i].s = read ();    cow[i].e = read ();        //读入外挂优化
             //scanf ("%d%d", &cow[i].s, &cow[i].e);
             cow[i].id = i;
             maxn = max (maxn, cow[i].e);
         }
         memset (ans, , sizeof (ans));
         sort (cow+, cow+n+, cmp);
         for (int i=; i<=n; ++i)
         {
             if (cow[i].e == cow[i-].e && cow[i].s == cow[i-].s)        //如果值相等，不加入统计
                 cnt[cow[i].id] = cnt[cow[i-].id];
             else
             {
                 cnt[cow[i].id] = sum (cow[i].s + );                    //第id的牛有多少比它强壮
             }
             plus (cow[i].s + );
         }
         int j;
         for (j=; j<n; ++j)
         {
             print (cnt[j]);    putchar (' ');        //输出外挂优化
             //printf ("%d ", cnt[j]);
         }
         printf ("%d\n", cnt[j]);
     }

     return ;
 }