uva 1347

看了佳爷才有思路的，这也是算法导论的dp课后练习--贴代码，用内置数组ac了，而思路相同的vector并没有过，在本地的两个测试样例都没有问题，不知道哪里出错，还用vector试了一下不等长的二维数组，结果wa，这里开心（捂胸口状

ac

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdio>

using namespace std;

const int maxn = 50 + 5;

float dist[maxn][maxn], d[maxn][maxn];
int x[maxn], y[maxn];

int main(void)
{
    int n;
    while (cin >> n)
    {
        for (int i = 0;i < n;i++)
            cin >> x[i] >> y[i];
        for (int i = 1;i < n;i++)
            for (int j = 0;j < i;j++)
                dist[i][j] = sqrt((x[i] - x[j])*(x[i] - x[j]) 
                    + (y[i] - y[j]) * (y[i] - y[j]));
        for (int i = 0;i < n - 1;i++)
            d[n - 1][i] = dist[n - 1][i];

        for (int i = n - 2;i > 0;i--)
            for (int j = 0;j < i;j++)
                d[i][j] = min(d[i + 1][j] + dist[i + 1][i],
                    d[i + 1][i] + dist[i + 1][j]);
        printf("%.2f
", d[1][0] + dist[1][0]);
    }
    return 0;
}

vector实现

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdio>

using namespace std;

vector<pair<int, int> > point;
int n;

int sumofsquare(int i, int j)
{
    int ix = point[i].first, iy = point[i].second;
    int jx = point[j].first, jy = point[j].second;

    return (ix - jx)*(ix - jx) + (iy - jy)*(iy - jy);
}

void calculate_dist(vector<vector<float> > &dist)
{
    dist.push_back(vector<float>());
    for (int i = 1;i < n;i++)
        dist.push_back(vector<float>(i));

    for (int i = 1;i < n;++i)
        for (int j = 0;j < i;j++)
        {
            float dis_ij = sqrt(sumofsquare(i, j));
            dist[i][j] = dis_ij;
        }
}

float dp(vector<vector<float> > &d, vector<vector<float> > &dist)
{
    d.push_back(vector<float>());
    for (int i = 1;i < n;i++)
        d.push_back(vector<float>(i));

    for (int i = 0;i < n - 1;i++)
        d[n - 1][i] = dist[n - 1][i];
    
    for(int i=n-2;i>0;i--)
        for (int j = 0;j < i;j++)
        {
            d[i][j] = min(d[i + 1][j] + dist[i + 1][i], d[i + 1][i] + dist[i + 1][j]);
        }
    return d[1][0] + dist[1][0];
}

int main(void)
{
    while (cin >> n&&n > 0)
    {
        point.clear();//记得这一步，一开始wa都不知道哪里出问题真的傻逼
        for (int i = 0;i < n;i++)
        {
            int x, y;
            cin >> x >> y;
            point.push_back(make_pair(x, y));
        }
        vector<vector<float> > dist;
        calculate_dist(dist);
        vector<vector<float> >d;
        printf("%.2f
", dp(d, dist));
    }
    return 0;
}

//这些怎么删除啊啊啊啊，原来代码贴在这