View Compilation Error

0_0_37759343_12547.cpp: In function 'int dfs(int, int)':
0_0_37759343_12547.cpp:31:9: error: 'P' was not declared in this scope
     if (P[x] == S[x + y - 1] && x  <= n) {
         ^
0_0_37759343_12547.cpp:31:17: error: 'S' was not declared in this scope
     if (P[x] == S[x + y - 1] && x  <= n) {
                 ^
0_0_37759343_12547.cpp:35:9: error: 'Q' was not declared in this scope
     if (Q[y] == S[x + y - 1] && y <= n) {
         ^
0_0_37759343_12547.cpp:35:17: error: 'S' was not declared in this scope
     if (Q[y] == S[x + y - 1] && y <= n) {
                 ^