hdu 1025 Constructing Roads In JGShining's Kingdom dp（LIS）

hdu 1025 Constructing Roads In JGShining's Kingdom

http://acm.hdu.edu.cn/showproblem.php?pid=1025

 

二分求最長上升子序列，長度即可建路數

 

//hdu 1025
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <map>
using namespace std;
const int maxn = 500010;
int dp[maxn], n, pos[maxn];
int dynamic(){
    int i, j, k, lef, rig, mid, len;
    dp[1] = pos[1];
    len = 1;
    for( i= 2; i<= n; i++){
        lef = 0;
        rig = len;
        while( lef <= rig){
            mid = (lef + rig) >> 1;
            if( dp[mid] > pos[i]) rig = mid - 1;
            else  lef = mid + 1;
        }
        dp[lef] = pos[i];
        if( lef > len) len ++;
    }
    return len;
}
int main(){
	//freopen("1.txt", "r", stdin);
	int i, j, k, aa, bb, cas= 1, tmp;
    while( scanf("%d", &n) != EOF){
        for( i= 1, tmp = 0; i<= n; i++){
            scanf("%d%d", &aa, &bb);
            pos[aa] = bb;
        }
        tmp = dynamic();
        if(tmp <= 1 )
            printf("Case %d:\nMy king, at most %d road can be built.\n\n", cas++, tmp);
        else
            printf("Case %d:\nMy king, at most %d roads can be built.\n\n", cas++, tmp);
    }
	return 0;
}