checkCode.java

public class checkCode {
static boolean check(String path) {
// first character of the path should always be from (F,B,L,R)
if(path.charAt(0)!='F' && path.charAt(0)!='B' && path.charAt(0)!='L' && path.charAt(0)!='R' ) {
return false;
}
// declare steps to count number of steps in a direction
// steps should not be greater than 99
int steps=0;
//iterate over the string to check its validity
for(int i=1;i<path.length();i++) {
char c = path.charAt(i);
// the current letter is from (F,B,L,R) or not
if(c=='F' || c=='B' || c=='L' || c=='R') {
// steps == 0 means last letter was also from (F,B,L,R)
// and no two letter from (F,B,L,R) can appear simultaneously
// steps > 99, but number of steps should be in range [1,99]
if(steps==0 || steps>99) return false;
else steps=0;
}
// c is some number from 0 to 9
else if(c>=0 && c<=9) {
steps += (c-'0');
}
// c is neither a number nor a letter from (F,B,L,R)
else {
return false;
}
}
// number of steps for the last move is valid or not
if(steps==0 || steps>99) return false;
// every condition is passed hence true
return true;
}
}