C ++程序通过使用堆栈检查均衡的身体
在这里，我们将讨论如何使用堆栈检查平衡括号。我们不仅检查打开和关闭支架，还检查支架的顺序。例如，我们可以说表达式“[[{}(){()}]]”是正确的，而表达式“{{}]”则是不正确的。
Input: Some expression with brackets "{()}[]"
Output: They are balanced算法
Step 1: Define a stack to hold brackets
Step 2: Traverse the expression from left to right
Step 2.1: If the character is opening bracket (, or { or [, then push it into stack
Step 2.2: If the character is closing bracket ), } or ] Then pop from stack, and if the popped character is matched with the starting bracket then it is ok. otherwise they are not balanced.
Step 3: After traversal if the starting bracket is present in the stack then it is not balanced.范例程式码
#include<iostream>
#include<stack>
using namespace std;
bool isBalanced(string expr) {
stack<char> s;
char ch;
for (int i=0; i<expr.length(); i++) { //for each character in the expression, check conditions
if (expr[i]=='('||expr[i]=='['||expr[i]=='{') { //when it is opening bracket, push into stack
s.push(expr[i]);
continue;
}
if (s.empty()) //stack cannot be empty as it is not opening bracket, there must be closing bracket
return false;
switch (expr[i]) {
case ')': //for closing parenthesis, pop it and check for braces and square brackets
ch = s.top();
s.pop();
if (ch=='{' || ch=='[')
return false;
break;
case '}': //for closing braces, pop it and check for parenthesis and square brackets
ch = s.top();
s.pop();
if (ch=='(' || ch=='[')
return false;
break;
case ']': //for closing square bracket, pop it and check for braces and parenthesis
ch = s.top();
s.pop();
if (ch =='(' || ch == '{')
return false;
break;
}
}
return (s.empty()); //when stack is empty, return true
}
main() {
string expr = "[{}(){()}]";
if (isBalanced(expr))
cout << "Balanced";
else
cout << "Not Balanced";
}输出结果
Balanced