8. String to Integer (atoi)

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 public static int myAtoi(String str) {        if(str == null || str.length() < 1) {            return 0;        }        int len = str.length();        double maxDou = 0;        boolean isPositive = true;        int find = -1;        int place1  = str.lastIndexOf('-');        int place2 = str.lastIndexOf('+');        if(place1 > place2) {            isPositive = false;            maxDou = Integer.MAX_VALUE*1.0 + 1;        }else {            maxDou = Integer.MAX_VALUE*1.0;        }        int resInt = 0;        double tmpDou = 0;        int i = 0;        boolean overflag =false;        for(i = 0 ;i < len; i++) {            if(resInt != 0) {                find =1;            }            char c = str.charAt(i);            if(((c == '+' || c == '-') && find == -1) || (c == '0'  && resInt == 0) || (c ==' ' && find == -1)) {                if((c == '+' || c == '-') && find == -1) {                    find = 1;                }                continue;            }else if(c >= '0' && c <= '9') {                tmpDou = tmpDou*10 + char2num(c);                if(tmpDou > maxDou) {                    resInt = isPositive?Integer.MAX_VALUE:Integer.MIN_VALUE;                    overflag = true;                    break;                }                resInt = resInt*10 + char2num(c);            }else{                break;            }        }       return overflag ?resInt:(isPositive?resInt:-resInt);    }    public static int char2num(char c) {        int i=0;        switch(c) {        case '0' :             i=0;            break;        case '1' :             i=1;            break;        case '2' :             i=2;            break;        case '3' :             i=3;            break;        case '4' :             i=4;            break;        case '5' :             i=5;            break;        case '6' :             i=6;            break;        case '7' :             i=7;            break;        case '8' :             i=8;            break;        case '9' :             i=9;            break;        }        return i;    }
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