//#pragma GCC optimize ("O3")
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
void solve() {
int n, k;
cin >> n >> k;
vector<int> x(k + 1), c(k + 1);
for (int i{1}; i <= k; ++i) cin >> x[i];
for (int i{1}; i <= k; ++i) cin >> c[i];
vector<char> ans(n);
char abc{'a'};
ans[0] = 'a', ans[1] = 'b', ans[2] = 'c';
x[0] = 3, c[0] = 3;
for (int i{1}; i <= k; ++i) {
if (x[i] - x[i - 1] < c[i] - c[i - 1]) return cout << "NO\n", []{}();
int i2{x[i - 1] + c[i] - c[i - 1]};
for (int j{x[i - 1]}; j < i2; ++j) ans[j] = 'c' + i;
for (int j{i2}; j < x[i]; ++j) ans[j] = abc, abc = (abc == 'c' ? 'a' : abc + 1);
}
cout << "YES\n";
for (int i{0}; i < n; ++i) cout << ans[i];
cout << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int t{1};
cin >> t;
while (t--) solve();
}
1715D - 2+ doors | 267A - Subtractions |
1582A - Luntik and Concerts | 560A - Currency System in Geraldion |
946A - Partition | 1068B - LCM |
1692E - Binary Deque | 679A - Bear and Prime 100 |
488A - Giga Tower | 14A - Letter |
1150A - Stock Arbitraging | 1552A - Subsequence Permutation |
1131F - Asya And Kittens | 1475F - Unusual Matrix |
133B - Unary | 1547A - Shortest Path with Obstacle |
624A - Save Luke | 1238A - Prime Subtraction |
1107C - Brutality | 1391B - Fix You |
988B - Substrings Sort | 312A - Whose sentence is it |
513A - Game | 1711E - XOR Triangle |
688A - Opponents | 20C - Dijkstra |
1627D - Not Adding | 893B - Beautiful Divisors |
864B - Polycarp and Letters | 1088A - Ehab and another construction problem |