feat: 逆波兰表达式

Author: haotf

Diff for: .gitignore

@@ -1,2 +1,3 @@
 .vscode
-log
+log
+node_modules

Diff for: 150.逆波兰表达式rpn.js

@@ -0,0 +1,96 @@
+const isOperator = (s) => ["+", "-", "*", "/"].includes(s);
+const parse = (expression) => {
+  const tokens = [];
+  for (let i = 0; i < expression.length; i++) {
+    let token = "";
+    if (isOperator(expression[i]) && isOperator(tokens[tokens.length - 1])) {
+      token = expression[i];
+      i++;
+    }
+    while (/\d/.test(expression[i])) {
+      token = token + expression[i];
+      i++;
+    }
+    if (token) {
+      tokens.push(Number(token));
+      i--;
+    } else {
+      if (expression[i] !== " ") {
+        tokens.push(expression[i]);
+      }
+    }
+  }
+  return tokens;
+};
+
+const transform = (tokens) => {
+  const operators = [];
+  const result = [];
+  for (let i = 0; i < tokens.length; i++) {
+    const ele = tokens[i];
+    if (typeof ele === "number") {
+      result.push(ele);
+    } else {
+      if (ele === "*" || ele === "/" || ele === "(") {
+        operators.push(ele);
+      } else if (operators[operators.length - 1] === "(") {
+        operators.push(ele);
+      } else if (ele === ")") {
+        while (operators[operators.length - 1] !== "(") {
+          result.push(operators.pop());
+        }
+        operators.pop();
+      } else {
+        while (operators.length > 0) {
+          result.push(operators.pop());
+        }
+        operators.push(ele);
+      }
+    }
+  }
+  while (operators.length > 0) {
+    result.push(operators.pop());
+  }
+  return result;
+};
+
+const calc = (tokens) => {
+  let stack = [];
+  for (let i = 0; i < tokens.length; i++) {
+    const ele = tokens[i];
+    if (typeof ele === "number") {
+      stack.push(ele);
+    } else {
+      const right = stack.pop();
+      const left = stack.pop();
+      switch (ele) {
+        case "+":
+          stack.push(left + right);
+          break;
+        case "-":
+          stack.push(left - right);
+          break;
+        case "*":
+          stack.push(left * right);
+          break;
+        case "/":
+          stack.push(left / right);
+          break;
+      }
+    }
+  }
+  return stack[0];
+};
+const rpn = (expression) => {
+  const tokens = parse(expression);
+  const result = transform(tokens);
+  const value = calc(result);
+  console.log(value);
+  return value;
+};
+
+rpn("12 + (7 - 3) * 2 + 9 / 3");
+
+rpn("((10 * (6 * ((9 + 3) * 11))) + 17) + 50");
+
+rpn("2 + 30 * (20 - 10) / (100 / 5)");

Diff for: package.json

@@ -0,0 +1,26 @@
+{
+  "name": "leetcode",
+  "version": "1.0.0",
+  "description": "leecode",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/coderhaotf/leetcode.git"
+  },
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/coderhaotf/leetcode/issues"
+  },
+  "homepage": "https://github.com/coderhaotf/leetcode#readme",
+  "devDependencies": {
+    "cz-conventional-changelog": "^3.3.0"
+  },
+  "config": {
+    "commitizen": {
+      "path": "./node_modules/cz-conventional-changelog"
+    }
+  }
+}