cf水题 --Duff and Weight Lifting

http://codeforces.com/contest/588/my

C. Duff and Weight Lifting

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Recently, Duff has been practicing weight lifting. As a hard practice, Malek gave her a task. He gave her a sequence of weights. Weight of i-th of them is 2wi pounds. In each step, Duff can lift some of the remaining weights and throw them away. She does this until there's no more weight left. Malek asked her to minimize the number of steps.

Duff is a competitive programming fan. That's why in each step, she can only lift and throw away a sequence of weights 2a1, ..., 2ak if and only if there exists a non-negative integer x such that 2a1 + 2a2 + ... + 2ak = 2x, i. e. the sum of those numbers is a power of two.

Duff is a competitive programming fan, but not a programmer. That's why she asked for your help. Help her minimize the number of steps.

Input

The first line of input contains integer n (1 ≤ n ≤ 106), the number of weights.

The second line contains n integers w1, ..., wn separated by spaces (0 ≤ wi ≤ 106 for each 1 ≤ i ≤ n), the powers of two forming the weights values.

Output

Print the minimum number of steps in a single line.

Sample test(s)

input

51 1 2 3 3

output

2

input

40 1 2 3

output

4

题目意思，给一个数n，下面有n个数wi，如果sum(2^wi)==2^x(x是整数），那么就给结果 ans 加一次，min（ans);;;

理解：

由于wi很大，无法表示2^wi,所以考虑到wi相等，k个wi=（wi+1）*k/2, k是偶数时，wi被完全合并，k是奇数时，ans++;遍历，由1---10^6+32;下面给出代码：

#include <iostream>#include <stdio.h>#include <string.h>using namespace std;const  int maxn=1000000+32;int a[maxn];int main(){    int n,ans,data;    while(scanf("%d",&n)!=-1)    {        memset(a,0,sizeof(a));        for(int i=0;i<n;i++)        {            scanf("%d",&data);            a[data]++;        }        ans=a[0]%2;        for(int i=1;i<maxn;i++)        {            a[i]=a[i-1]/2+a[i];            if(a[i]%2==1)            ans++;        }        printf("%d\n",ans);    }    ///cout << "Hello world!" << endl;    return 0;}