luogu P2439 [SDOI2005]阶梯教室设备利用

题目链接

luogu P2439 [SDOI2005]阶梯教室设备利用

题解

dp

代码

#include<vector>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
inline int read() {
    int x = 0,f = 1;char c = getchar();
    while(c < '0'||c > '9')c = getchar();
    while(c <= '9' &&c >= '0')x = x * 10 + c - '0',c = getchar();
    return x * f;
} 
const int maxn = 30007;
int l[maxn],r[maxn];
int n,dp[maxn];
std::vector<int>vec[maxn];
int mx = 0;
int main() {
    n = read();
    for(int i = 1;i <= n;++ i) {
        l[i] = read();r[i] = read();
        vec[r[i]].push_back(l[i]);
        mx = std::max(mx,r[i]);
    }
    for(int i = 1;i <= mx;++ i) {
        dp[i] = dp[i - 1];
        for(int j = 0;j < vec[i].size();++ j) {
            dp[i] = std::max(dp[i],dp[vec[i][j]] + (i - vec[i][j]));
        }
    }
    printf("%d\n",dp[mx]);
    return 0;
}