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Commit823401c

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accepted for StringToInteger
1 parenta6f9f5a commit823401c

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+50
-11
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1 file changed

+50
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‎EASY/src/easy/StringToInteger.java

Lines changed: 50 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -21,6 +21,9 @@
2121
2222
If no valid conversion could be performed, a zero value is returned. If the correct value is out of the range of representable values, INT_MAX (2147483647) or INT_MIN (-2147483648) is returned.*/
2323
publicclassStringToInteger {
24+
//TODO: look at others' solutions
25+
26+
//Eventually, made it AC'ed, lots of corner cases, but now, really felt much easier and the though process is super clear than the first time I tried to solve it which was 3~4 years ago from now. 8/9/2016
2427
publicintmyAtoi(Stringstr) {
2528
//case 1: str is greater than Integer.MAX_VALUE, return Integer.MAX_VALUE as the question states it
2629

@@ -42,12 +45,22 @@ public int myAtoi(String str) {
4245
char[]chars =str.toCharArray();
4346
StringBuildersb =newStringBuilder();
4447
booleannegative;
48+
intminuSignCount =0,plusSignCount =0;
4549
inti =0;
46-
if(chars[0] =='-') {
47-
negative =true;
48-
i++;//let i start from 1 in this case
50+
while(i <chars.length){
51+
if(chars[i] =='-'){
52+
minuSignCount++;
53+
i++;
54+
}elseif(chars[i] =='+'){
55+
plusSignCount++;
56+
i++;
57+
}else {
58+
break;
59+
}
4960
}
50-
elsenegative =false;
61+
if((plusSignCount >0 &&minuSignCount >0) ||minuSignCount >1 ||plusSignCount >1)return0;
62+
negative =minuSignCount%2 !=0;
63+
if(i >=chars.length)return0;
5164

5265
//it might be a floating number, so consider '.'
5366
intperiod =0;
@@ -57,6 +70,8 @@ public int myAtoi(String str) {
5770
sb.append(chars[i++]);
5871
}
5972

73+
if(sb ==null ||sb.length() ==0)return0;
74+
6075
intresult =0;
6176
if(period >0){
6277
//use Double to parse
@@ -66,20 +81,44 @@ public int myAtoi(String str) {
6681
System.out.println(e);
6782
}
6883
}else {
69-
//use Integer to parse
70-
try{
71-
result =Integer.parseInt(sb.toString());
72-
}catch(Exceptione){
73-
System.out.println(e);
74-
}
84+
//use Long to parse to handle integer overflow case
85+
longtemp =0;
86+
if(sb.length() >=Long.toString(Long.MAX_VALUE).length() &&negative){
87+
returnInteger.MIN_VALUE;
88+
}elseif(sb.length() >=Long.toString(Long.MAX_VALUE).length() && !negative){
89+
returnInteger.MAX_VALUE;
90+
}else {
91+
try{
92+
temp =Long.parseLong(sb.toString());
93+
}catch(Exceptione){
94+
if(sb.length() >=Integer.MAX_VALUE)result =Integer.MAX_VALUE;
95+
}
96+
if(temp > (long)Integer.MAX_VALUE+1) {
97+
if(!negative)returnInteger.MAX_VALUE;
98+
elsereturnInteger.MIN_VALUE;
99+
}
100+
elseif(temp == (long)Integer.MAX_VALUE+1 &&negative)returnInteger.MIN_VALUE;
101+
elseif(temp == (long)Integer.MAX_VALUE+1)returnInteger.MAX_VALUE;
102+
elseif(temp <Integer.MIN_VALUE)result =Integer.MIN_VALUE;
103+
elseresult = (int)temp;
104+
}
75105
}
76106

107+
if(negative)result = -result;
77108
returnresult;
78109
}
79110

80111
publicstaticvoidmain(String...strings){
81112
StringToIntegertest =newStringToInteger();
82-
Stringstr ="1";
113+
// String str = "2147483648";
114+
// String str = "+-2";//a really interesting test case, you never know how stupid one's input could be like, this is to challenge your program to be more robust. It's expecting to return 0 for this case which means it's not a valid number
115+
// String str = "+";
116+
// String str = "abc";
117+
// String str = "1";
118+
// String str = "-2147483648";
119+
// String str = "++1";//I'm really amazed by OJ's test case variety, it's expecting 0 in this case
120+
// String str = "-2147483649";
121+
Stringstr ="9223372036854775809";
83122
System.out.println(test.myAtoi(str));
84123

85124

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