#include <bits/stdc++.h>
​
int main() {
    // freopen("in", "r", stdin);
    int ttt;
    std::cin >> ttt;
    while (ttt--) {
        int n, m;
        std::cin >> n >> m;
        std::vector<int> fa(n + 1), dsu(n + 1);
        int dfn_tot = 0, bel_tot = 0;
        std::vector<int> dfn(n + 1), low(n + 1), dep(n + 1), bel(n + 1);
        std::vector<std::vector<int>> ver(n + 1), diff(n + 1);
        std::vector<bool> vis(n + 1);
        std::string c;
        std::cin >> c;
        for (int i = 0, u, v; i < m; ++i) {
            std::cin >> u >> v; ++u, ++v;
            if (c[u - 1] == c[v - 1]) {
                diff[u].emplace_back(v);
                diff[v].emplace_back(u);
            } else {
                ver[u].emplace_back(v);
                ver[v].emplace_back(u);
            }
        }
​
        auto tarjan = [&] (auto self, const int u, const int pre = -1) -> void {
            dfn[u] = low[u] = ++dfn_tot;
            vis[u] = true;
            for (auto &&v: ver[u]) {
                if (!dfn[v]) {
                    fa[v] = u;
                    self(self, v, i);
                    low[u] = std::min(low[u], low[v]);
                } else if (i != (pre ^ 1)) {
                    low[u] = std::min(low[u], dfn[v]);
                }
            }
        };
        auto shrink = [&] (auto self, const int u) -> void {
            bel[u] = bel_tot;
            for (auto &&v: ver[u]) {
                if (bel[v] == 0 && low[v] <= dfn[u]) {
                    self(self, v);
                }
            }
        };
​
        tarjan(tarjan, 1);
        for (int i = 1; i <= n; ++i) {
            if (dfn[i] != 0 && bel[i] == 0) {
                ++bel_tot;
                shrink(shrink, i);
            }
        }
        
        bool flag{false};
        for (int i = 1; i <= n; ++i)
            dsu[i] = i;
        auto GetFa = [&] (auto self, const int u) -> int {
            return dsu[u] == u ? u : dsu[u] = self(self, dsu[u]);
        };
        auto dfs = [&] (auto self, const int u) -> void {
            vis[u] = true;
            for (auto &&v: diff[u]) {
                if (vis[v]) {
                    if (dfn[u] == 0 || dfn[v] == 0) {
                        continue;
                    }
                    int w = GetFa(GetFa, v);
                    if (u == w || v == w) {
                        flag = true;
                    }
                    if (bel[fa[w]] == bel[u] || bel[fa[w]] == bel[v]) {
                        flag = true;
                    }
                }
            }
            for (auto &&v: ver[u]) {
                if (!vis[v]) {
                    self(self, v);
                }
            }
            dsu[u] = fa[u];
        };
        dfs(dfs, 1);
        puts(flag ? "yes" : "no");
    }
    return 0;
}

answer.code:2:1: error: ‘​’ does not name a type
    2 | ​
      |