LeetCode 274

H-Index

Given an array of citations (each citation is a non-negative integer)
of a researcher, write a function to compute the researcher's h-index.

According to the definition of h-index on Wikipedia:
"A scientist has index h if h of his/her N papers have
at least h citations each, and the other N ? h papers have
no more than h citations each."

For example, given citations = [3, 0, 6, 1, 5],
which means the researcher has 5 papers in total and each of them
had received 3, 0, 6, 1, 5 citations respectively.
Since the researcher has 3 papers with at least 3 citations each
and the remaining two with no more than 3 citations each,
his h-index is 3.

Note:

If there are several possible values for h,
the maximum one is taken as the h-index.

Hint:

An easy approach is to sort the array first.
What are the possible values of h-index?
A faster approach is to use extra space.

/*************************************************************************
> File Name: LeetCode274.c
> Author: Juntaran
> Mail: JuntaranMail@gmail.com
> Created Time: Thu 19 May 2016 20:47:36 PM CST
************************************************************************/

/*************************************************************************

H-Index

Given an array of citations (each citation is a non-negative integer)
of a researcher, write a function to compute the researcher's h-index.

According to the definition of h-index on Wikipedia:
"A scientist has index h if h of his/her N papers have
at least h citations each, and the other N ? h papers have
no more than h citations each."

For example, given citations = [3, 0, 6, 1, 5],
which means the researcher has 5 papers in total and each of them
had received 3, 0, 6, 1, 5 citations respectively.
Since the researcher has 3 papers with at least 3 citations each
and the remaining two with no more than 3 citations each,
his h-index is 3.

Note:

If there are several possible values for h,
the maximum one is taken as the h-index.

Hint:

An easy approach is to sort the array first.
What are the possible values of h-index?
A faster approach is to use extra space.

************************************************************************/

#include "stdio.h"

void quick_sort( int* nums, int left, int right )
{
if( left < right )
{
int i = left;
int j = right;
int flag = nums[left];

while( i < j )
{
while( i<j && nums[j]>=flag )    // 从右向左找第一个小于x的数
{
j--;
}
if( i < j )
{
nums[i++] = nums[j];
}

while( i<j && nums[i]<flag )    // 从左向右找第一个大于等于x的数
{
i++;
}
if( i < j )
{
nums[j--] = nums[i];
}
}
nums[i] = flag;
quick_sort( nums, left, i-1 );
quick_sort( nums, i+1, right);
}
}

void printfNums( int* nums, int numsSize )
{
int i;
for( i=0; i<numsSize; i++ )
{
printf("%d ", nums[i]);
}
printf("\n");
}

int hIndex(int* citations, int citationsSize)
{

quick_sort( citations, 0, citationsSize-1 );

int i;
for( i=0; i<citationsSize; i++ )
{
if( (citationsSize-i) <= citations[i] )
{
return citationsSize-i;
}
}
return 0;
}

int main()
{
int citations[] = {9,8,7,6,5,4,3,2,1};
int citationsSize = 9;
int left = 0;
int right = 8;

printfNums( citations, citationsSize );
quick_sort( citations, left, right );
printfNums( citations, citationsSize );

int ret = hIndex( citations, citationsSize );
printf("%d\n", ret);

return 0;
}