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生成四则运算的题目
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <style> | |
| #result{ | |
| width:900px; | |
| line-height:25px; | |
| } | |
| #result ol li { | |
| width:30%; | |
| float:left; | |
| } | |
| </style> | |
| <style> | |
| @media print { | |
| #control { | |
| display:none; | |
| } | |
| #result { | |
| margin-top:20px; | |
| font-size:18px; | |
| } | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <script> | |
| var operators = ["+", "-", "*", "/"]; | |
| var mulOperators = ['*', '/']; | |
| var opMap = { | |
| '+' : ' + ', | |
| '-' : ' - ', | |
| '*' : ' × ', | |
| '/' : ' ÷ ' | |
| }; | |
| var minNumber = 1; | |
| var maxNumber = 100; | |
| function translateOp(op){ | |
| return opMap[op]; | |
| } | |
| function genNumber(min, max) { | |
| return Math.floor(Math.random() * (max - min) + min); | |
| } | |
| function genOperator() { | |
| var index = genNumber(0, 4); | |
| return operators[index]; | |
| } | |
| function isInt(n) { | |
| return n % 1 === 0; | |
| } | |
| function isResultValidNumber(parts){ | |
| var expr = parts.join(""); | |
| var ret = eval(expr); | |
| return (ret >= minNumber && ret < maxNumber && isInt(ret)); | |
| } | |
| function isValidExpr(parts){ | |
| if (mulOperators.indexOf(parts[1]) == -1 | |
| && mulOperators.indexOf(parts[3]) >= 0){ // first op is not */, second op is * / | |
| return isResultValidNumber(parts.slice(2, 5)) && isResultValidNumber(parts); | |
| } | |
| else{ | |
| return isResultValidNumber(parts.slice(0, 3)) && isResultValidNumber(parts); | |
| } | |
| } | |
| function genExpr(){ | |
| while (1){ | |
| var parts = [ | |
| genNumber(minNumber, maxNumber), | |
| genOperator(), | |
| genNumber(minNumber, maxNumber), | |
| genOperator(), | |
| genNumber(minNumber, maxNumber), | |
| ]; | |
| if(isValidExpr(parts)){ | |
| var expr = parts.join(""); | |
| var ret = eval(expr); | |
| parts.push(' = '); | |
| parts.push(ret); | |
| return parts; | |
| } | |
| } | |
| } | |
| function genPuzzle(){ | |
| var expr = genExpr(); | |
| var location = genNumber(0, 4) * 2; | |
| expr[location] = '( )'; | |
| expr[1] = opMap[expr[1]]; | |
| expr[3] = opMap[expr[3]]; | |
| return expr.join(""); | |
| } | |
| function genPaper(count, targetId){ | |
| var target = document.getElementById(targetId); | |
| var text = ["<ol>"]; | |
| for(var i = 0; i < count; ++i){ | |
| text.push("<li>" + genPuzzle() + "</li>"); | |
| } | |
| text.push("</ol>"); | |
| target.innerHTML = text.join("\n");; | |
| } | |
| function gen(){ | |
| var count = parseInt(document.getElementById('count').value); | |
| genPaper(count, 'result'); | |
| } | |
| </script> | |
| <div id="control"> | |
| 题目数量： <input type="text" id="count" value="75" /> | |
| <button onclick="gen();">生成题目</button> | |
| </div> | |
| <div id="result" > | |
| </div> | |
| </body> | |
| </html> |
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