整形字符串转数字（INT） - 越界判断

算法

#include <stdio.h>
#include <string.h>
const int INT_MAX = 2147483647;
const int INT_MIN = (-INT_MAX - 1);
const int MAXS = 1e5 + 1;
char S[MAXS];
int len;
int char2int(char c){
    return (int)(c - '0');
}
int main(){
    scanf("%s", S);
    len = strlen(S);
    int sum = 0;
    bool negative = false;
    bool overbound = false;
    if(S[0] == '-'){
        negative = true;
    }
    else if(S[0] <= '9' && S[0] >= '0'){
        sum += char2int(S[0]);
    }
    for(int i=1; i< len; i++){
        if(S[i] <= '9' && S[i] >= '0'){
            int t = char2int(S[i]);
            // 判断是否越界
            if(negative == false){
                if(sum > INT_MAX / 10){
                    overbound = true;
                    sum = INT_MAX;
                    break;
                }
                sum *= 10;
                if(INT_MAX - sum < t){
                    overbound = true;
                    sum = INT_MAX;
                    break;
                }
                sum += t;
            }else{
                if(sum < INT_MIN / 10){
                    overbound = true;
                    printf("1-------\n");
                    sum = INT_MIN;
                    break;
                }
                sum *= 10;
                if(INT_MIN - sum > -t){
                    overbound = true;
                    sum = INT_MIN;
                    break;
                }
                sum -= t;
            }
        }
        else{
            break;
        }
    }
    printf("%d\n", sum);
}