[POJ 3171] Cleaning Shifts

[题目链接]
[算法]
线段树 + dp
[代码]
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 100010
const int INF = 2e9;

struct info
{
    int l,r,s;
} a[MAXN];

int i,n,m,e;

struct SegmentTree
{
    struct Node
    {
        int l,r;
        int mn;
    } Tree[MAXN<<2];
    inline void build(int index,int l,int r)
    {
        int mid;
        Tree[index].l = l;
        Tree[index].r = r;
        Tree[index].mn = INF;
        if (l == r) return;
        mid = (l + r) >> 1;
        build(index<<1,l,mid);
        build(index<<1|1,mid+1,r);
    }
    inline void pushup(int index)
    {
        Tree[index].mn = min(Tree[index<<1].mn,Tree[index<<1|1].mn);
    }
    inline void update(int index,int pos,int val)
    {
        int mid;
        if (Tree[index].l == Tree[index].r)
        {
            Tree[index].mn = min(Tree[index].mn,val);
            return;
        }
        mid = (Tree[index].l + Tree[index].r) >> 1;
        if (mid >= pos) update(index<<1,pos,val);
        else update(index<<1|1,pos,val);
        pushup(index);
    }
    inline int query(int index,int l,int r)
    {
        int mid;
        if (Tree[index].l == l && Tree[index].r == r) return Tree[index].mn;
        mid = (Tree[index].l + Tree[index].r) >> 1;
        if (mid >= r) return query(index<<1,l,r);
        else if (mid + 1 <= l) return query(index<<1|1,l,r);
        else return min(query(index<<1,l,mid),query(index<<1|1,mid+1,r));
    } 
} T;
inline bool cmp(info a,info b)
{
    return a.r < b.r;
}

int main()
{
    
    scanf("%d%d%d",&n,&m,&e);
    for (i = 1; i <= n; i++) scanf("%d%d%d",&a[i].l,&a[i].r,&a[i].s);
    sort(a+1,a+n+1,cmp);
    T.build(1,m-1,e);
    T.update(1,m-1,0);
    for (i = 1; i <= n; i++)
    {
        if (a[i].r < m)    continue;
        T.update(1,a[i].r,T.query(1,a[i].l-1,a[i].r-1)+a[i].s);
    }
    if (T.query(1,e,e) != INF) printf("%d
",T.query(1,e,e));
    else printf("-1
");
    
    return 0;
}