为啥TLE?(dfs代码求调)awa

#include <bits/stdc++.h>
using namespace std;

int n, a, b;
int num[201];
bool vis[201];
int ans = -1;

void dfs(int x, int dep) {
	if (x == b) {
		if (ans == -1 || dep < ans) {
			ans = dep;
		}
		return;
	}
	int u = x + num[x];
	if (u <= n && !vis[u]) {
		vis[u] = true;
		dfs(u, dep + 1);
		vis[u] = false;
	}
	int d = x - num[x];
	if (d >= 1 && !vis[d]) {
		vis[d] = true;
		dfs(d, dep + 1);
		vis[d] = false;
	}
}

int main() {
	memset(vis, false, sizeof(vis));
	cin >> n >> a >> b;
	for (int i = 1; i <= n; i++) {
		cin >> num[i];
	}
	vis[a] = true;
	dfs(a, 0);
	cout << ans << endl;
	return 0;
}