剑指05替换空格.md

方法一：

直接新建数组然后遍历添加。注意转换成byte

func replaceSpace(s string) string {
    res := make([]byte, 0)
    for _, v := range s {
        if v == ' ' {
            res = append(res, []byte("%20")...)
        } else {
            res = append(res, byte(v))
        }
    }
    return string(res)
}

方法二：扩展原数组

func replaceSpace(s string) string {
    // 计算空格数量
    count := 0
    b := []byte(s)
    for _, v := range b {
        if v == ' ' {
            count++
        }
    }
    oldLen := len(b)
    newLen := 2 * count
    temp := make([]byte, newLen)
    b = append(b, temp...)
    i := oldLen - 1
    j := oldLen + newLen - 1
    for i >= 0 {
        if b[i] == ' ' {
            b[j] = '0'
            b[j-1] = '2'
            b[j-2] = '%'
            j -= 2
        } else {
            b[j] = b[i]
        }
        i--
        j--
    }
    return string(b)
}