Codeforces Round #486-F.Rain and Umbrellas题解

一、题目链接：http://codeforces.com/contest/988/problem/F

二、题面

三、思路

　　很明显而且比较能想到的$dp$。

四、代码实现

#include<bits/stdc++.h>
using namespace std;
#define fst first
#define snd second
#define MAXN 2018
typedef pair<int, int> PII;
typedef long long LL;
int dest, n, m, p[MAXN], rain_len[MAXN];
PII rains[MAXN];
map<int, int> mp;
bool wet[MAXN];
LL b[MAXN], dp[MAXN][MAXN];
int main(){
//    freopen("input.txt", "r", stdin);
    int t1, t2;
    scanf("%d%d%d", &dest, &n, &m);
    ;i <= n;++i){
        scanf("%d%d", &t1, &t2);
        rains[i] = make_pair(t1, t2);
        fill(wet + t1, wet + t2, true);
    }
    sort(rains + , rains + n + );
    ;i <= m;++i){
        scanf("%d%d", &t1, &t2);
        if(mp.find(t1) != mp.end())mp[t1] = min(mp[t1], t2);
        else mp[t1] = t2;
    }
    m = ;
    for(auto e : mp){
        t1 = e.fst, t2 = e.snd;
        b[++m] = t2, p[m] = t1;
    }
    b[m + ] = , p[m + ] = dest;
    ;i <= m;++i){
        ];j > p[i];--j){
            ]){
                rain_len[i] = j - p[i];
                break;
            }
        }
    }
    ;
    ;i < p[];++i)dry &= !wet[i];
    if(!dry)return !printf("-1\n");
    else{
        memset(dp, 0x3f, sizeof(dp));
        dp[][] = ;
        ;i <= m;++i){
            ;j <= i;++j){
                dp[i + ][i + ] = min(dp[i + ][i + ], dp[i][j] + b[j] * rain_len[i]);
                dp[i + ][j] = min(dp[i + ][j], dp[i][j] + b[j] * (p[i + ] - p[i]));
            }
        }
        LL ans = *min_element(dp[m + ], dp[m + ] + MAXN + );
        cout << ans << endl;
    }
    ;
}