一道题目，原位置替换字符串

#include <iostream>
#include <string>

void change_word(char *a, int len) {
    if (a == NULL) {
        return;
    }
    int count = 0;
    for (int i=0; i<len; i++) {
        if (a[i] == ‘ ‘) {
            count+=2;
        }
    }

    int newi = len + count - 1;
    for (int i=len-1; i>=0; i--) {
        if (a[i] != ‘ ‘) {
            a[newi--] = a[i];
        }
        else {
            a[newi--] = ‘3‘;
            a[newi--] = ‘2‘;
            a[newi--] = ‘1‘;
        }
    }
    return;
}

int main() {
    std::cout << "Hello, World!" << std::endl;

    char ch[100];
    strncpy(ch, "hi hi hihihi hi", 16);
    std::cout << ch << std::endl;

    change_word(ch, 16);
    std::cout << ch << std::endl;

    return 0;
}

#include <iostream>
#include <string>

void change_word(char *a) {
    if (a == NULL) {
        return;
    }

    int newi = 0;
    int i = 0;
    while (a[i] != ‘\0‘) {
        if (i==0 || a[i] != a[i-1]) {
            if (newi != i) {
                a[newi] = a[i];
            }
            newi++;
        }
        i++;
    }
    a[newi] = ‘\0‘;

    return;
}

int main() {
    std::cout << "Hello, World!" << std::endl;

    char ch[100];
    strncpy(ch, "hi hhi hiiiiihhhihi hi", 23);
    std::cout << ch << std::endl;

    change_word(ch);
    std::cout << ch << std::endl;

    return 0;
}