package Interview;

import java.util.HashMap;

import java.util.Map;

/**

* 确定有限状态机

*/

public class StringToInt_8 {

class AutoState{

public int sign=1;

public long ans=0;

private String state="start";

private Map<String,String[]> stateTable=new HashMap<String,String[]>(){

{

put("start",new String[]{"start","sign","in_number","end"});

put("sign",new String[]{"end","end","in_number","end"});

put("in_number",new String[]{"end","end","in_number","end"});

put("end",new String[]{"end","end","end","end"});

}

};

public int get(char c){

state=stateTable.get(state)[getCol(c)];

if("in_number".equals(state)){

ans=10*ans+c-'0';

ans=sign==1? Math.min(ans,(long)Integer.MAX_VALUE):Math.min(ans,-(long)Integer.MIN_VALUE);

}else if("sign".equals(state)){

sign=c=='+'?1:-1;

}

return "end".equals(state)?-1:0;

}

private int getCol(char c){

if(c==' '){

return 0;

}else if(c=='+'||c=='-'){

return 1;

}else if(Character.isDigit(c)){

return 2;

}else{

return 3;

}

}

}

public int myAtoi(String s) {

AutoState autoState=new AutoState();

if(s==null||s.length()==0) return 0;

char[] str = s.toCharArray();

for(int i=0;i<s.length();i++){

int i1 = autoState.get(str[i]);

if(i1==-1) break;

}

return (int)(autoState.sign* autoState.ans);

}

}