ural 1090. In the Army Now

樹狀數組的wiki頁面：http://zh.wikipedia.org/wiki/%E6%A0%91%E7%8A%B6%E6%95%B0%E7%BB%84

題意：給出士兵的身高站位求逆序數，本題中是求某人前面比他矮的人的個數和。

#include <iostream>#include <cstdio>#include <cstring>using namespace std;const int N = 10007;int c[N], n;int lowbit(int i) {    return i&(-i);}void add(int i, int val) {    while(i <= n)     {        c[i] += val;        i += lowbit(i);    }}int sum(int i) {    int s = 0;    while(i > 0)     {        s += c[i];        i -= lowbit(i);    }    return s;}int main() {    int k, s, max, i, j, x, max_f;    while(~scanf("%d%d", &n, &k))    {        max = 0; max_f = 1;        for(i = 0; i < k; i++)         {            memset(c, 0, sizeof(c));            for(s = 0, j = 0; j < n; j++)            {                scanf("%d", &x);                x = n - x + 1;                add(x, 1);                s += sum(x-1);            }            if(s > max)    {max = s; max_f = i+1;}        }        cout << max_f << endl;    }    return 0;}