LeetCode劍指Offer面試題05. 替換空格

請實現一個函數，把字符串 s 中的每個空格替換成"%20"。

 

示例 1：

輸入：s = "We are happy."
輸出："We%20are%20happy."

 

限制：

0 <= s 的長度 <= 10000

char* replaceSpace(char* s){
    int n = strlen(s),num_char=0,num_space=0;
    for(int i = 0;i<n;i++){
        if(s[i]==' '){
            ++num_space;
        }
        else{
            ++num_char;
        }
    }
    int length = num_char+num_space*3;
    char *res = (char*)malloc(sizeof(char)*(length+1));
    res[length] = '\0';
    int p1 = n-1, p2 = length-1;
    while(p1>=0){
        if(s[p1]!=' '){
            res[p2--]=s[p1--];
        }
        else if(s[p1]==' '){
            res[p2--]='0';
            res[p2--]='2';
            res[p2--]='%';
            p1--;
        }
    }
    return res;
}

 res[length] = '\0';這一行一定要加，否則在leetcode運行時會heap-buffer-overflow