“模拟”专项类型题

 public String modifyString(String ss) {
        char[] s = ss.toCharArray();

        int n = s.length;
        for(int i = 0; i < n; i++){
            if(s[i] == '?'){
                for(char ch = 'a'; ch <= 'z'; ch++){
                    if((i == 0 || ch != s[i-1]) && (i == n-1 || ch != s[i+1])){
                        s[i] = ch;
                        break;
                    }
                }
            }
        }

        return String.valueOf(s);
    }

 public int findPoisonedDuration(int[] timeSeries, int duration) {
        int ret = 0;
        for(int i = 1; i < timeSeries.length; i++){
            int x = timeSeries[i] - timeSeries[i-1];
            if(x < duration) ret += x;
            else ret += duration;
        }

        return ret+duration;
    }

public static String convert(String ss, int numRows) {
        if(numRows == 1){
            return ss;
        }

        char[] s = ss.toCharArray();

        String[] array = new String[numRows];
        Arrays.fill(array, "");//上面默认会赋值null，这里要赋值一下

        //方向变量向下行数+1； 方向变量向上行数-1
        boolean down = false;
        for(int i = 0,row = 0; i < s.length; i++){
            array[row] += s[i];

            //如果方向到第一行或者最后一行，要改变
            if(row == 0 || row == numRows-1){
                down = !down;
            }
            row += down ? 1 : -1;
        }

        StringBuilder stringBuilder = new StringBuilder();
        for(String x : array){
            stringBuilder.append(x);
        }

        return stringBuilder.toString();
    }

//方法二：
     public static String convert(String ss, int numRows) {
        if(numRows == 1) return ss;

        char[] s = ss.toCharArray();
        int d = 2 * numRows - 2;
        int n = s.length;

        StringBuilder ret = new StringBuilder();

        //1.处理第一行
        for(int i = 0; i < n; i+=d)
            ret.append(s[i]);

        //2.枚举处理中间行
        for(int k = 1; k < numRows-1; k++)
            for(int i = k, j = d-i; i < n || j < n; i += d,j += d){
                if(i < n) ret.append(s[i]);
                if(j < n) ret.append(s[j]);
            }

        //1.处理最后一行
        for(int i = numRows-1; i < n; i+=d)
            ret.append(s[i]);


        return ret.toString();          
    }

 public String countAndSay(int n) {
        
        String ret = "1";

            //描述,n-1次即可
        for(int i = 1; i < n; i++){
            StringBuilder tmp = new StringBuilder();

            //具体的描述
            int len = ret.length();
            for(int left = 0, right = 0; right < len; ){

                while(right < len && ret.charAt(right) == ret.charAt(left)) right++;

                tmp.append(Integer.toString(right-left));
                tmp.append(ret.charAt(left));
                left = right;
            }
            
            ret = tmp.toString();
        }

        return ret;
    }

 public int minNumberOfFrogs(String c) {
        char[] croakOfFrogs = c.toCharArray();
        String t = "croak";
        int n = t.length();
        int[] hash = new int[n]; // 数组模拟哈希表


        //再new一个哈希表来绑定，某个元素和下标关系
        Map<Character,Integer> index = new HashMap<>();
        for(int i = 0; i < n; i++)
            index.put(t.charAt(i),i);


        for(char ch : croakOfFrogs){
            if(ch == t.charAt(0)){
                if(hash[n-1] != 0) hash[n-1]--;
                hash[0]++;
            }else{
                int i = index.get(ch);
                if(hash[i-1] == 0) return -1;
                hash[i-1]--; hash[i]++;
            }
        }

        for(int i = 0; i <= n-2; i++)
            if(hash[i] != 0)
                return -1;

        return hash[n-1];           
    }