刚接触背包问题，求指教

#include<iostream>
#include<stdio.h>
#include<cstring>
#define MAXN 1000+1
using namespace std;
int f[MAXN][MAXN]={0};
int utime[101]={0};
int vaule[101]={0};
int dp(int ,int );
int max(int a,int b)
{
    if(a>=b)
    return a;
    else
    return b;
}
int main()
{
    int amount=0;
    int ttime=0;
    memset(f,0,sizeof(f));
    cin>>ttime>>amount;
    for(int i=1;i<=amount;++i)
    {
        scanf("%d %d",&utime[i],&vaule[i]);
    }
    cout<<dp(amount,ttime)<<endl;
}
int dp(int x,int y)
{
    for(int row=1;row<=x;++row)
    for(int coulmn=y;coulmn>=0;--coulmn)
    {
        if(y>=utime[row])
        f[row][coulmn]=max(f[row-1][coulmn-utime[row]]+vaule[row],f[row-1][coulmn]);
        else
        f[row][coulmn]=f[row-1][coulmn];
    }
    return f[x][y];
}
[/codec]