poj1769 Minimizing maximizer

poj1769 Minimizing maximizer

总之，存代码 = =

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
const int MAXN = 500000+10;
const int MAXM = 500000+10;
const int INF = 0x7ffffff;
int seg[MAXN<<1];
void init(int l,int r,int x){
    if(l == r){
        seg[x] = INF;
        return;
    }
    int mid = (l+r)>>1;
    init(l,mid,x<<1);
    init(mid+1,r,x<<1|1);
    seg[x] = INF;
}
void upd(int l,int r,int x,int k,int v){
    if(l == r){
        if(l == k){
            seg[x] = v;
        }
        return;
    }
    int mid = (l+r)>>1;
    if(k>= l && k <= mid){
        upd(l,mid,x<<1,k,v);
    }
    if(k>mid && k<=r){
        upd(mid+1,r,x<<1|1,k,v);
    }
    seg[x] = min(seg[x<<1],seg[x<<1|1]);
}
int quercy(int l,int r,int x,int L,int R){
    if(l>=L && r<=R){
        return seg[x];
    }
    int mid = (l+r)>>1;
    int v = INF;
    if(mid >= L){
        v = min(v,quercy(l,mid,x<<1,L,R));
    }
    if(mid < R){
        v = min(v,quercy(mid+1,r,x<<1|1,L,R));
    }
    return v;
}
int n,m;
int s[MAXM],t[MAXM];
int dp[MAXN];
void solve(){
    init(1,n,1);
    fill(dp,dp+n+1,INF);
    dp[1] = 0;
    upd(1,n,1,1,0);
    for(int i=0; i<m; i++){
        int v = min(dp[ t[i] ],quercy(1,n,1,s[i],t[i])+1);
        dp[t[i]] = v;
        upd(1,n,1,t[i],v);
    }
    printf("%d\n",dp[n]);
}
int main(){
//    freopen("input.txt","r",stdin);
    while(~scanf("%d%d",&n,&m)){
        for(int i = 0;i< m;i++){
            scanf("%d%d",&s[i],&t[i]);
        }
        solve();
    }
    return 0;
}