poj 2481 Cows——树状数组&&python

题意：有$n$头牛，每只牛都有一个范围值$[S, E]$，如果对于牛i和牛j来说，它们的测验值满足下面的条件则证明牛i比牛j强壮：$S_i \leq S_j \ and \ E_j \leq E_i \  and \ E_i-S_i > E_j-S_j$。请输出每头牛有几头牛比其强壮。

分析：

我们可以对$S$按从小到大排序，$E$按从大到小排序

如果当前所求的$i$的$s[i]==s[i-1] \ and \ e[i]==e[i-1]$,那么$ans[i]=ans[i-1]$,

否则便是查询排序后在他前面的牛的$e$大于等于他的数目(可以利用树状数组去维护)

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

const int maxn = 100000 + 10;

struct Node{
    int s, e, id;
}cows[maxn];
int C[maxn], num, ans[maxn], n;

bool cmp(Node a, Node b)
{
    if(a.s == b.s)  return a.e > b.e;
    else  return a.s < b.s;
}

int lowbit(int x)
{
    return x & -x;
}
int sum(int x)
{
    int ret = 0;
    while (x > 0)
    {
        ret += C[x];
        x -= lowbit(x);
    }
    return ret;
}
void add(int x, int d)
{
    while (x <= num)
    {
        C[x] += d;
        x += lowbit(x);
    }
}

int main()
{
    while(scanf("%d", &n) == 1 && n)
    {
        num = 0;
        for(int i = 0;i < n;i++)
        {
            scanf("%d%d", &cows[i].s, &cows[i].e);
            cows[i].id = i;
            num = max(num, cows[i].e);
        }
        sort(cows, cows+n, cmp);
        memset(C,0,sizeof(C));
        for(int i = 0;i < n;i++)
        {
            if(i == 0)  ans[cows[i].id] = 0;
            if(cows[i].s == cows[i-1].s && cows[i].e == cows[i-1].e)
                ans[cows[i].id] = ans[cows[i-1].id];
            else
                ans[cows[i].id] = i - sum(cows[i].e-1);
            add(cows[i].e, 1);
        }
        for(int i = 0;i < n;i++)
            printf("%d%c", ans[i], i == n-1 ? '\n' : ' ');
    }
    return 0;
}
/*
3
1 1
1 2
2 3
*/

python，结构体排序用list模拟

import functools

maxn = 100000 + 10;
C = [0]*maxn
num = 0
ans = [0]*maxn
n = 0

def cmp(a, b):
    if a[0] == b[0]:  
        if a[1] > b[1]:
            return -1
        elif a[1] < b[1]:
            return 1
        else:
            return 0
    else:  
        if a[0] < b[0]:
            return -1
        else:
            return 1

def lowbit(x):
    return x & -x

def sum(x):
    ret = 0
    while x > 0:
        ret += C[x]
        x -= lowbit(x)
    return ret

def add(x, d):
    while x <= num:
        C[x] += d
        x += lowbit(x)

while(True):    
    n = int(input().strip())
    if n == 0:
        break
    num = 0
    cows = [[0 for col in range(3)] for row in range(n)]
    for i in range(n):
        cows[i][0], cows[i][1] = map(int, input().strip().split())
        cows[i][2] = i
        num = max(num, cows[i][1])
    
    cows = sorted(cows, key=functools.cmp_to_key(cmp))
    #print(cows)
    for i in range(0, num+1):  C[i] = 0
    for i in range(n):
        if i == 0:  ans[cows[i][2]] = 0
        if cows[i][0] == cows[i-1][0] and cows[i][1] == cows[i-1][1]:
            ans[cows[i][2]] = ans[cows[i-1][2]]
        else:
            ans[cows[i][2]] = i - sum(cows[i][1]-1)
        add(cows[i][1], 1)
    
    for i in range(n):
        print(ans[i])