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友谊圈(Easy)

http://ch.vijos.org/Contest/%E3%80%8CAdera%203%E3%80%8D%E6%9D%AF%E7%9C%81%E9%80%89%E6%A8%A1%E6%8B%9F%E8%B5%9B/Problem/Show/%E5%8F%8B%E8%B0%8A%E5%9C%88(Easy)

错误的dp初始化代码

View Code
#include<stdio.h>
#include<string.h>
int a[20100];
int dp[20100];
int main()
{
    int n,max,m;
    int  i,j;
    while(scanf("%d",&n)!=EOF&&n!=0)
    {
        memset(dp,0,sizeof(dp));
        memset(a,0,sizeof(a));
        for(i=1;i<=n;i++)
        scanf("%d",&a[i]);
        dp[1]=1;
        max=1;
        for(i=2;i<=n;i++)
        {
            m=0;
            for(j=i-1;j>=1;j--)
            {
                if(a[j]+i-j<=a[i])
                {
                    if(m<dp[j])m=dp[j];
                    //break;
                }
            }
            dp[i]=m+1;
            //if(j==0)dp[i]=1;
            //
            //dp[i]=;
        }
        for(i=2;i<=n;i++)
        //printf("%d\n",dp[i]);
        if(dp[i]>max)max=dp[i];
        printf("%d\n",max);
    }
    return 0;
}

求最长递增子序列的和+小变形

Dp问题dp数组的初始化很重要!!!!!!!!!!!!!

再呈上精简代码一份:
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxn = 20010;
int n;
int data[maxn], a[maxn];
int main()
{
    int i, j, ans ;
    while(cin>>n)
    {
        ans=0;
        for(i = 1; i <= n; i++)
        {
            scanf("%d", &a[i]);
            if(a[i] >= i) data[i] = 1;
            else data[i] = -1e9;
        }
        data[1] = 1;
        for(i = 2; i <= n; i++)
        {
            for(j = 1; j < i; j++) if(a[i]-a[j] >= i-j) data[i] = max(data[i], data[j]+1);
            ans = max(ans, data[i]);
        }
        cout<<ans<<endl;
    }
    return 0;
}

 

posted on 2013-05-07 22:52  雨钝风轻  阅读(222)  评论(0编辑  收藏  举报