AcWing 2816. 判断子序列

题目连接

https://www.acwing.com/problem/content/2818/

思路

双指针扫描，一个指向A，一个指向B，然后匹配成功就都往后移否则，b往后移动，注意一下边界情况就行，我在这RE了好几次

#include
using namespace std;
#define ll long long
#define mod 1000000009
#define endl "\n"
#define PII pair

int dx[4]={0,-1,0,1},dy[4]={-1,0,1,0};

ll ksm(ll a,ll b) {
	ll ans = 1;
	for(;b;b>>=1LL) {
		if(b & 1) ans = ans * a % mod;
		a = a * a % mod;
	}
	return ans;
}

ll lowbit(ll x){return -x & x;}

const int N = 2e6+10;
int n,m,a[N],b[N];

int main()
{
	cin>>n>>m;
	for(int i = 1;i >a[i];
	for(int j = 1;j >b[j];
	int l = 1,r = 1;
	while(true) {
		if(a[l] == b[r]){
			if(l == n){
				puts("Yes");
				return 0;
			}
			l++;
			r++;
		}else r++;
		if(l > n || r > m) break;
	}
	puts("No");
	
	return 0;
}