Rain and Umbrellas(dp)

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题目链接 http://codeforces.com/problemset/problem/988/F

令dp[i][j]为走到目标为i处,手里拿着第j把伞,同时注意,在某处可能存在不止一把伞

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
#include <stack>
#include <cstdlib>
#include <iomanip>
#include <cmath>
#include <cassert>
#include <ctime>
#include <map>
#include <set>
using namespace std;
#pragma comment(linker, "/stck:1024000000,1024000000")
#define lowbit(x) (x&(-x))
#define max(x,y) (x>=y?x:y)
#define min(x,y) (x<=y?x:y)
#define MAX 100000000000000000
#define MOD 1000000007
#define pi acos(-1.0)
#define ei exp(1)
#define PI 3.1415926535897932384626433832
#define ios() ios::sync_with_stdio(true)
#define INF 0x3f3f3f3f
#define mem(a) (memset(a,0,sizeof(a)))
typedef long long ll;
int dp[2006][2006],a,n,m;
int rain[2006],umbre[2006];
int val[2006],pos[2006];
int main()
{
    scanf("%d%d%d",&a,&n,&m);
    memset(rain,0,sizeof(rain));
    memset(umbre,0,sizeof(umbre));
    a++;
    for(int i=0,x,y;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        for(int j=x+1;j<=y;j++)
            rain[j]=1;
    }
    for(int i=1,x,y;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        x++;
        pos[i]=x;
        val[i]=y;
        if(!umbre[x] || (umbre[x] && y<val[umbre[x]]))
            umbre[x]=i;
    }
    memset(dp,INF,sizeof(dp));
    dp[0][0]=0;
    for(int i=0;i<a;i++)
    {
        for(int j=0;j<=m;j++)
        {
            if(pos[j]>i) continue;
            if(j) dp[i+1][j]=min(dp[i+1][j],dp[i][j]+val[j]);
            if(!rain[i]) dp[i+1][0]=min(dp[i+1][0],dp[i][j]);
            if(umbre[i]) dp[i+1][umbre[i]]=min(dp[i+1][umbre[i]],dp[i][j]+val[umbre[i]]);//同一个点可能存在多个雨伞
        }
    }
    int ans=INF;
    for(int i=0;i<=m;i++)
        ans=min(ans,dp[a][i]);
    printf("%d\n",ans>=INF?-1:ans);
    return 0;
}

 

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