7-23洛谷做题记录

7-23洛谷做题记录

P1359 租用游艇
DP求或最短路

#include <bits/stdc++.h>
using namespace std;
int f[210],i,j,k,n;
int main()
{
	cin >> n;
	for(int i = 1 ; i <= n ; i ++ )
		for(int j = i + 1; j <= n ; j ++ )
		{
			cin >> k;
			if(f[i] == 0 || f[i] + k < f[j])
			{
				f[j] = f[i] + k;
			}
		}
	cout << f[n];
}

P1434 [SHOI2002] 滑雪
记忆化搜索

#include <bits/stdc++.h>

using namespace std;
const int fx[] = {1,-1,0,0};
const int fy[] = {0,0,-1,1};
int R,C;
int g[110][110];
int s[110][110];




bool check(int x,int y)
{
	return x >= 1 && x <= R && y >= 1 && y <= C ;
}



int dfs(int x,int y)
{
	if(s[x][y])return s[x][y];
	s[x][y] = 1;
	for(int i = 0 ; i < 4 ; i ++ )
	{
		int xx = x + fx[i],yy = y + fy[i];
		if(check(xx,yy)&&g[xx][yy]<g[x][y])
		{
			dfs(xx,yy);	
			s[x][y] = max(s[x][y],s[xx][yy] + 1);
			
		}
		
	}
	return s[x][y];
}

int main()
{
	cin >> R >> C;
	for(int i = 1 ; i <= R ; i ++ )
		for(int j = 1 ; j <= C ; j ++ )
		cin >> g[i][j];
		
	int res = 0;
	for(int i = 1 ; i <= R ; i ++ )
		for(int j = 1 ; j <= C  ; j ++ )
		res = max(dfs(i,j),res);
		
	cout << res << endl;
	return 0;
}

枚举对角线

#include <stdio.h>
#include <stdbool.h>

int n, ans;
int x[510], y[510];
bool vis[510][510];
int main(){
	n = read();
	for(int i = 1; i <= n; ++i){
		x[i] = read();
		y[i] = read();
		x[i] = (x[i] + 51) << 1;
		y[i] = (y[i] + 51) << 1;
		vis[x[i]][y[i]] = 1;
	}
	for(int i = 1; i < n; ++i)
		for(int j = i + 1; j <= n; ++j){
            int midx = (x[i] + x[j]) >> 1;
            int midy = (y[i] + y[j]) >> 1;  
                      
            int x1 = midx - (midy - y[i]);
            if(x1 <= 0) continue;
            
            int y1 = midy + (midx - x[i]);
            if(y1 <= 0) continue;
            
            int x2 = midx + (midy - y[i]); 
            if(x2 <= 0) continue;
            int y2 = midy - (midx - x[i]);
            if(y2 <= 0) continue; 
            if(vis[x1][y1] && vis[x2][y2]) ++ans;
        }
	printf("%d\n", ans >> 1);
	return 0;
}