http://acm.swust.
#include<stdio.h>
void main()
{
    long long a,b,c[2000001],d[2000001]={0},t,i,j,max,m=0;
    scanf("%lld",&a);
    for(i=0;i<a;i++)
        scanf("%lld",&c[i]);
    for(i=0;i<a;i++)
        for(j=i+1;j<a;j++)
            if(c[i]>c[j])
            {
                b=c[j];
                c[j]=c[i];
                c[i]=b;
            }
            for(i=0;i<a;i++)
                for(j=i;j<a;j++)
                    if(c[i]==c[j])
                        d[i]++;
                    for(i=0,max=d[m];i<a;i++)
                        if(max<d[i])
                        {
                            max=d[i];
                            m=i;
                        }
                        printf("%lld\n",c[m]);
}

时间超时了呗，你看看你那循环，愁~~

#include <stdio.h>

int a[2000001],n,i,j;

int main()
{
    memset(a,0,sizeof(a));
    for (i=(scanf("%d",&n),n);i>0;i--) a[(scanf("%d",&j),j)]++;
    for (i=1,j=0; i<=2000000; i++) j=(a[i]>a[j])?i:j;
    printf("%d\n",j);
}