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: [e-mail]
     > 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- );
         quick_sort( nums, i+, right);
     }
 }

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

 int hIndex(int* citations, int citationsSize)
 {

     quick_sort( citations, , citationsSize- );

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

 int main()
 {
     int citations[] = {,,,,,,,,};
     int citationsSize = ;
     int left = ;
     int right = ;

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

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

     return ;
 }