Ural 1028. Stars(树状数组)

题目链接:点击打开链接

思路:

为了满足第一个条件, 我们可以先按照x坐标排序,  然后我们用树状数组来维护y坐标大小关系, 就可以在O(nlogn)的时间内求出答案了。

细节参见代码:

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define Max(a,b) ((a)>(b)?(a):(b))
#define Min(a,b) ((a)<(b)?(a):(b))
using namespace std;
typedef long long ll;
typedef long double ld;
const double eps = 1e-6;
const double PI = acos(-1);
const int mod = 1000000000 + 7;
const int INF = 0x3f3f3f3f;
// & 0x7FFFFFFF
const int seed = 131;
const ll INF64 = ll(1e18);
const int maxn = 15111;
int T,n,m,bit[32111],len,ans[maxn];
struct node {
    int x, y;
    node(int x=0, int y=0):x(x), y(y) {}
    bool operator < (const node& rhs) const {
        if(x != rhs.x) return x < rhs.x;
        else return y < rhs.y;
    }
}a[maxn];
void add(int x, int d) {
    while(x <= len) {
        bit[x] += d;
        x += x & -x;
    }
}
int sum(int x) {
    int ans = 0;
    while(x > 0) {
        ans += bit[x];
        x -= x & -x;
    }
    return ans;
}
int main() {
    while(~scanf("%d",&n)) {
        memset(bit, 0, sizeof(bit));
        len = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d%d", &a[i].x, &a[i].y);
            a[i].x++; a[i].y++;
            ans[i-1] = 0;
            len = max(len, a[i].y);
        }
        sort(a+1, a+n+1);
        for(int i = 1; i <= n; i++) {
            int cur = sum(a[i].y);
            ans[cur]++;
            add(a[i].y, 1);
        }
        for(int i = 0; i < n; i++) printf("%d\n", ans[i]);
    }
    return 0;
}


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