78 lines
2.2 KiB
PHP
78 lines
2.2 KiB
PHP
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<?php
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// 四则运算 +-*/()
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function expression($str)
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{
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$str = str_replace(' ','',$str);
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$arr = preg_split('/([\+\-\*\/\(\)])/', $str, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
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$numStack = []; // 存放数字
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$operStack = []; // 存放运算符
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$operStack[] = NULL;
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for ($i = 0; $i < count($arr); $i++){
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if (ord($arr[$i]) >= 48 && ord($arr[$i] <= 57)){
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array_push($numStack, $arr[$i]);
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continue;
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}
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switch ($arr[$i]){
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case '+':
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case '-':
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$arrLen = count($operStack);
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while ($operStack[$arrLen-1] === '*' || $operStack[$arrLen-1] === '/' || $operStack[$arrLen-1] === '-'){
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compute($numStack, $operStack);
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$arrLen--;
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}
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array_push($operStack, $arr[$i]);
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break;
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case '*':
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case '/':
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case '(':
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array_push($operStack, $arr[$i]);
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break;
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case ')':
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$arrLen = count($operStack);
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while ($operStack[$arrLen-1] !== '('){
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compute($numStack, $operStack);
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$arrLen--;
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}
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array_pop($operStack);
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break;
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default:
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throw new \Exception("不支持的运算符", 1);
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break;
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}
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}
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$arrLen = count($operStack);
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while ($operStack[$arrLen-1] !== NULL){
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compute($numStack, $operStack);
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$arrLen--;
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}
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echo array_pop($numStack);
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}
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//数字栈长度减一，运算符栈长度减一
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function compute(&$numStack, &$operStack){
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$num = array_pop($numStack);
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switch (array_pop($operStack)) {
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case '*':
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array_push($numStack, array_pop($numStack) * $num);
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break;
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case '/':
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array_push($numStack, array_pop($numStack) / $num);
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break;
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case '+':
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array_push($numStack, array_pop($numStack) + $num);
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break;
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case '-':
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array_push($numStack, array_pop($numStack) - $num);
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break;
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}
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}
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expression('-1+2-(1+2*3)');
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echo PHP_EOL;
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eval('echo -1+2-(1+2*3);');
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