就是栋gg上课提到的那个，觉得自己做得好烦哪~

代码如下：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

/*function declarations*/
void intToStr(int, char*);
void addNegativeSign(char*);

int main(void)
{
    int n;
    printf("Enter an integer (valid range from -2^31 to 2^31 - 1): ");
    scanf("%d",&n);
    /*since 32-bit integer has most 10 digits, we declare the char array with length of 12*/
    /*10 to hold the value, 1 to hold the ending '\0' and the left is optional to minus sign*/
    char str[12];
    intToStr(n,str);
    printf(str);
}

void intToStr(int n, char* s)
{
    int digits = 0;
    int tempInt = n;
    int flag = 0;
    
    /*first, determine whether the number if positive or negative*/
    if(n < 0){
        n = -n;
        flag = 1;
    }
    
    /*sicne an integer has at least 1 digit, we use the do-while loop*/
    do{
        digits++;
        tempInt /= 10;
    }while(tempInt);
    
    /*allocate essential space for characters needed*/
    char* p = (char *)(malloc(sizeof(char) * (digits+((flag)?2:1))));
    
    /*we form the string from the end, which is synchronized to the modulus operation*/
    char* q;
    for(q = p + digits - 1;q >= p;q--){
        tempInt = n % 10;
        *q = (char)(tempInt) + '0';
        n /= 10;
    }
    q = p + digits;
    *q = '\0';/*set the end char for the sake of safety*/
    
    /*if the number is negative, we need to add the negative sign*/
    if(flag){
        addNegativeSign(p);
    }
    
    strcpy(s,p);
    free(p);/*release the space allocated formerly*/
}

/*this function does not do boudary checing!*/
/*but since we had allocated enough space, it is at least safe to call it from the function above*/
void addNegativeSign(char* s){
    char* ss = s;
    while(*ss != '\0') ss++;
    ss++;
    while(ss > s){
        *ss = *(ss-1);
        ss--;
    }
    *s = '-';
}

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