文章目录
-
- 原题题目
- 代码实现（首刷自解）
- 代码实现（二刷自解 DAY 195 C++）
- 代码实现（三刷自解 DAY 279 C++）
- 代码实现（四刷自解 DAY 5 Golang）
原题题目
代码实现（首刷自解）
class Solution {
public:int myAtoi(string s) {
bool neg = false,wrong = false,numend = false,dealnum = false;;long ret = 0;int numdeal = -1;for(int i=0;i<s.size();++i){
char chr = s[i];if(chr != ' ' && chr != '-' && chr != '+' && (chr > '9' || chr < '0')){
wrong = true;break;}if(chr == ' ') continue;else if(chr == '-' || chr == '+' || (chr >= '0' && chr <= '9')){
if(chr == '-') neg = true;numdeal = i;if(chr == '-' || chr == '+') ++numdeal;break;} }if(numdeal == -1) wrong = true;for(int i=numdeal;!wrong && i<s.size();++i){
char chr = s[i];if(chr < '0' || chr > '9') {
if(numend) wrong = true;else numend = true;break;}else{
ret *= 10;ret += (chr - '0');if(ret > INT_MAX){
if(neg) ret = INT_MIN;else ret = INT_MAX;dealnum = true;break;}}}if(!dealnum) ret = (neg) ? -ret : ret; if(wrong) ret = 0;return (int)ret;}
};
代码实现（二刷自解 DAY 195 C++）
class Solution {
public:int myAtoi(string s) {
bool neg_flag = false,num_flag = false;int pos;long ret = 0;for(pos = 0;pos < s.size();++pos){
char chr = s[pos];if(chr == ' ' || chr == '-' || chr == '+' || isdigit(chr)){
if(chr == ' ') continue;if(isdigit(chr)) num_flag = true;else {
if(chr == '-') neg_flag = true;++pos;}break;}else return 0;}long int_min = -static_cast<long>(INT_MIN);for( ;pos < s.size();++pos){
char chr = s[pos];if(!isdigit(chr)) break;if(ret <= int_min){
ret *= 10;ret += (chr - '0');}else break;}if(neg_flag) ret = -ret;ret = (ret <= INT_MIN ? INT_MIN : ret);ret = (ret >= INT_MAX ? INT_MAX : ret);return ret;}
};
代码实现（三刷自解 DAY 279 C++）
class Solution {
public:int myAtoi(string s) {
int pos = 0, size = s.size();bool neg = false;for (; pos < size; ++pos) {
auto chr = s[pos];if (chr == ' ' || chr == '+' || chr == '-' || isdigit(chr)) {
if (chr == ' ') {
continue;} else {
if (chr == '-' || chr == '+') {
neg = (chr == '-');++pos;}break;}} else {
return 0;}}if (pos == size) return 0;int ret = 0;for (; pos < size; ++pos) {
auto chr = s[pos];if (!isdigit(chr)) {
break;}if (neg && abs((INT_MIN + (s[pos] - '0')) / 10) < ret ||((INT_MAX - (s[pos] - '0')) / 10) < ret) {
if (neg) {
ret = INT_MIN;} else {
ret = INT_MAX;}break;} else {
ret *= 10;ret += s[pos] - '0';}}if (neg && ret != INT_MIN) ret = -ret;return ret;}
};
代码实现（四刷自解 DAY 5 Golang）
func myAtoi(s string) int {
if len(s) == 0 {
return 0}neg, pos := false, 0size := len(s)for pos < size && s[pos] == ' ' {
pos++}if pos < size && (s[pos] == '+' || s[pos] == '-') {
if s[pos] == '-' {
neg = true}pos++}var ret int32 = 0const INT_MAX int32 = int32(^uint32(0) >> 1)const INT_MIN int32 = ^INT_MAXfor pos < size {
if s[pos] < '0' || s[pos] > '9' {
break}num := int32(s[pos] - '0')if neg == false && (INT_MAX - num) / 10 < ret {
ret = INT_MAXbreak}if neg == true && (INT_MIN + num) / 10 > ret {
ret = INT_MINbreak}ret *= 10if neg {
ret -= num} else {
ret += num}pos++}return int(ret)
}