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The longest ascending subsequence model acwing 1012 Sister cities

2022-07-07 14:13:00 【T_ Y_ F666】

Longest ascending subsequence model AcWing 1012. Friendly city

Original link

Algorithm tags

DP linear DP Longest ascending subsequence

Ideas

Sort friendly cities at one end , The longest ascending sequence at the other end is the answer
Insert picture description here

Code

#include<bits/stdc++.h>
#define int long long
#define rep(i, a, b) for(int i=a;i<b;++i)
#define Rep(i, a, b) for(int i=a;i>=b;--i)
using namespace std;
const int N = 5005, INF = 0x3f3f3f3f;
int f[N], f1[N], a[N];
inline int read(){
   int s=0,w=1;
   char ch=getchar();
   while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
   while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
   return s*w;
}
void put(int x) {
    if(x<0) putchar('-'),x=-x;
    if(x>=10) put(x/10);
    putchar(x%10^48);
}
struct Node{
    int a,b;
}node[N];
bool cmp(Node A, Node B){
    return A.b<B.b; 
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n=read(),ans=0;
	rep(i, 0, n){
	    node[i].a=read(),node[i].b=read(); 
	}
	sort(node, node+n, cmp);
	rep(i, 0, n){
	    f[i]=1;
	    rep(j, 0, i){
	        if(node[j].a<node[i].a){
	            f[i]=max(f[i], f[j]+1);
	        }
	    }
	    ans=max(ans, f[i]);
	}
	printf("%lld\n", ans);
}

y Master code

#include <algorithm>

using namespace std;

typedef pair<int, int> PII;

const int N = 5010;

int n;
PII city[N];
int f[N];

int main()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) scanf("%d%d", &city[i].first, &city[i].second);
    sort(city, city + n);

    int res = 0;
    for (int i = 0; i < n; i ++ )
    {
        f[i] = 1;
        for (int j = 0; j < i; j ++ )
            if (city[i].second > city[j].second)
                f[i] = max(f[i], f[j] + 1);
        res = max(res, f[i]);
    }

    printf("%d\n", res);

    return 0;
}