顺序遍历，栈，用 reduce / array_reduce / stream().reduce / Aggregate / accumulate 累积完成 1 行解，3 解法求解《1598. 文件夹操作日志搜集器》，

var minOperations = function(logs) {
  let r = 0
  for (let i = 0; i < logs.length; i++) {
    if (logs[i] === '../') {
      if (r > 0) r--
    } else if (logs[i] !== './') r++
  }
  return r
};

function minOperations(logs: string[]): number {
  let r = 0
  for (let i = 0; i < logs.length; i++) {
    if (logs[i] === '../') {
      if (r > 0) r--
    } else if (logs[i] !== './') r++
  }
  return r
};

class Solution {
  function minOperations($logs) {
    $r = 0;
    foreach ($logs as $log) {
      if ($log === '../') {
        if ($r > 0) $r--;
      } elseif ($log !== './') {
        $r++;
      }
    }
    return $r;
  }
}

func minOperations(logs []string) int {
  r := 0
  for _, log := range logs {
    if log == "../" {
      if r > 0 {
        r--
      }
    } else if log != "./" {
      r++
    }
  }
  return r
}

class Solution {
  public int minOperations(String[] logs) {
    int r = 0;
    for (String log : logs) {
      if (log.equals("../")) {
        if (r > 0) r--;
      } else if (log.compareTo("./") != 0) r++;
    }
    return r;
  }
}

public class Solution {
  public int MinOperations(string[] logs) {
    int r = 0;
    foreach (string log in logs) {
      if (log == "../") {
        if (r > 0) r--;
      } else if (log != "./") r++;
    }
    return r;
  }
}

int minOperations(char ** logs, int logsSize){
  int r = 0;
  for (int i = 0; i < logsSize; i++) {
    if (strcmp(logs[i], "../") == 0) {
      if (r > 0) r--;
    } else if (strcmp(logs[i], "./") != 0) {
      r++;
    }
  }
  return r;
}

class Solution {
public:
  int minOperations(vector<string>& logs) {
    int r = 0;
    for (string log : logs) {
      if (log == "../") {
        if (r > 0) r--;
      } else if (log != "./") r++;
    }
    return r;
  }
};

class Solution:
  def minOperations(self, logs: List[str]) -> int:
    r = 0
    for _, log in enumerate(logs):
      if log == "../": 
        if r > 0: r -= 1
      elif log != "./": r += 1
    return r

var minOperations = function(logs) {
  return logs.reduce((r, log) => log === '../' && r > 0 ? r - 1 : log !== '../' && log !== './' ? r + 1 : r, 0)
};

function minOperations(logs: string[]): number {
  return logs.reduce((r, log) => log == '../' && r > 0 ? r - 1 : log == '../' || log == './' ? r : r + 1, 0)
};

func minOperations(logs []string) int {
  return Reduce(logs, func(r int, log string) int {
    if log == "../" && r > 0 {
      return r - 1
    }
    if log == "../" || log == "./" {
      return r
    }
    return r + 1
  }, 0)
}
func Reduce(slice []string, cb func(prev int, cur string) int, initialValue int) int {
  prev := initialValue
  for _, cur := range slice {
    prev = cb(prev, cur)
  }
  return prev
}

class Solution {
  function minOperations($logs) {
    return array_reduce($logs, function($r, $log) {
      return $log == '../' && $r > 0 ? $r - 1 : ($log != '../' && $log != './' ? $r + 1 : $r);
    }, 0);
  }
}

class Solution {
  public int minOperations(String[] logs) { // 需累积器和组合器共同使用
    return Arrays.stream(logs).reduce(0, (r, log) -> log.equals("../") && r > 0 ? r - 1 : log.equals("../") || log.equals("./") ? r : r + 1, (r0, r1) -> r0 + r1);
  }
}

public class Solution {
  public int MinOperations(string[] logs) {
   return logs.Aggregate(0, (r, log) => log == "../" && r > 0 ? r - 1 : log != "../" && log != "./" ? r + 1 : r);
  }
}

class Solution {
public:
  int minOperations(vector<string>& logs) {
    return accumulate(logs.begin(), logs.end(), 0, [](int r, string log) -> int {
      return log == "../" && r > 0 ? r - 1 : log != "../" && log != "./" ? r + 1 : r;
    });
  }
};

class Solution:
  def minOperations(self, logs: List[str]) -> int:
    return reduce(lambda r, log : r - 1 if log == '../' and r > 0 else r + 1 if log != '../' and log != './' else r, logs, 0)

var minOperations = function(logs) {
  const stack = []
  for (let i = 0; i < logs.length; i++) {
    if (logs[i] === '../') {
      if (stack.length) stack.pop()
    } else if (logs[i] !== './') stack.push(logs[i])
  }
  return stack.length
};

function minOperations(logs: string[]): number {
  const stack = []
  for (let i = 0; i < logs.length; i++) {
    if (logs[i] === '../') {
      if (stack.length) stack.pop() 
    } else if (logs[i] !== './') stack.push(logs[i])
  }
  return stack.length
};

class Solution {
  function minOperations($logs) {
    $stack = [];
    foreach ($logs as $log) {
      if ($log === '../') {
        if (count($stack) > 0) array_pop($stack);
      } elseif ($log !== './') {
        $stack []= $log;
      }
    }
    return count($stack);
  }
}

func minOperations(logs []string) int {
  stack := []string{}
  for _, log := range logs {
    if log == "../" {
      if len(stack) > 0 {
        stack = stack[:len(stack) - 1]
      }
    } else if log != "./" {
      stack = append(stack, log)
    }
  }
  return len(stack)
}

class Solution {
  public int minOperations(String[] logs) {
    Deque<String> stack = new ArrayDeque<String>();
    for (String log : logs) {
      if (log.compareTo("../") == 0) {
        if (stack.isEmpty() == false) stack.pop();
      } else if (log.equals("./") == false) stack.push(log);
    }
    return stack.size();
  }
}

public class Solution {
  public int MinOperations(string[] logs) {
    Stack<string> stack = new Stack<string>();
    foreach (string log in logs) {
      if (log == "../") {
        if (stack.Count > 0) stack.Pop();
      } else if (log != "./") stack.Push(log);
    }
    return stack.Count;
  }
}

int minOperations(char ** logs, int logsSize){
  int* stack = malloc(sizeof(int) * 1e3);
  int pos = 0;
  for (int i = 0; i < logsSize; i++) {
    if (strcmp(logs[i], "../") == 0) {
      if (pos > 0) pos--;
    } else if (strcmp(logs[i], "./") != 0) stack[pos++] = logs[i];
  }
  return pos;
}

class Solution {
public:
  int minOperations(vector<string>& logs) {
    stack<string> st;
    for (string log : logs) {
      if (log == "../") {
        if (st.empty() == false) st.pop();
      } else if (log != "./") st.push(log);
    }
    return st.size();
  }
};

class Solution:
  def minOperations(self, logs: List[str]) -> int:
    stack = []
    for _, log in enumerate(logs):
      if log == "../":
        if len(stack) > 0: stack.pop()
      elif log != "./": stack.append(log)
    return len(stack)