poj 2299(离散化+树状数组)
2016-07-09 10:16
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Ultra-QuickSort
Description
In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. For the input sequence
9 1 0 5 4 ,
Ultra-QuickSort produces the output
0 1 4 5 9 .
Your task is to determine how many swap operations Ultra-QuickSort needs to perform in order to sort a given input sequence.
Input
The
input contains several test cases. Every test case begins with a line
that contains a single integer n < 500,000 -- the length of the input
sequence. Each of the the following n lines contains a single integer 0
≤ a[i] ≤ 999,999,999, the i-th input sequence element. Input is
terminated by a sequence of length n = 0. This sequence must not be
processed.
Output
For
every input sequence, your program prints a single line containing an
integer number op, the minimum number of swap operations necessary to
sort the given input sequence.
Sample Input
Sample Output
Source
题意:求解一个串的逆序数的个数是多少??
题解:离散化数组变成下标,然后每次将离散化的下标放进树状数组,放进去之后统计小于他的数的个数是多少。用 i - getsum(a[i])即为大于它的数的个数,其中 i 为当前已经插入的数的个数。
Time Limit: 7000MS | Memory Limit: 65536K | |
Total Submissions: 53777 | Accepted: 19766 |
In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. For the input sequence
9 1 0 5 4 ,
Ultra-QuickSort produces the output
0 1 4 5 9 .
Your task is to determine how many swap operations Ultra-QuickSort needs to perform in order to sort a given input sequence.
Input
The
input contains several test cases. Every test case begins with a line
that contains a single integer n < 500,000 -- the length of the input
sequence. Each of the the following n lines contains a single integer 0
≤ a[i] ≤ 999,999,999, the i-th input sequence element. Input is
terminated by a sequence of length n = 0. This sequence must not be
processed.
Output
For
every input sequence, your program prints a single line containing an
integer number op, the minimum number of swap operations necessary to
sort the given input sequence.
Sample Input
5 9 1 0 5 4 3 1 2 3 0
Sample Output
6 0
Source
题意:求解一个串的逆序数的个数是多少??
题解:离散化数组变成下标,然后每次将离散化的下标放进树状数组,放进去之后统计小于他的数的个数是多少。用 i - getsum(a[i])即为大于它的数的个数,其中 i 为当前已经插入的数的个数。
#include <iostream> #include <stdio.h> #include <string.h> #include <stack> #include <vector> #include <algorithm> using namespace std; const int N = 500005; struct Node{ int v,id; }node ; int a ,c ,n; int lowbit(int x){ return x&(-x); } void update(int idx,int v){ for(int i=idx;i<=N;i+=lowbit(i)){ c[i]+=v; } } int getsum(int idx){ int sum = 0; for(int i=idx;i>=1;i-=lowbit(i)){ sum+=c[i]; } return sum; } int cmp(Node a,Node b){ return a.v<b.v; } int main() { while(scanf("%d",&n)!=EOF,n){ memset(c,0,sizeof(c)); for(int i=1;i<=n;i++){ scanf("%d",&node[i].v); node[i].id = i; } sort(node+1,node+n+1,cmp); for(int i=1;i<=n;i++){ a[node[i].id] = i; } long long cnt = 0; for(int i=1;i<=n;i++){ update(a[i],1); cnt=cnt+ i - getsum(a[i]); } printf("%lld\n",cnt); } return 0; }
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