JavaScript上万关键字瞬间匹配
- hliang
- 0
- Posted on
既然考虑的是那种极端的关键字搜索，通常的逐个遍历搜索显然是行不通的。如今用的是JavaScript，若不使用Hash表实在是太对不起这门语言了。有着对表特天独厚的支持，不妨就拿出少量的空间来换取大量的时间吧。
代码在下面：
var treeSearch = {
makeTree: function(strKeys) {
'use strict';
var tblCur = {},
tblRoot,
key,
str_key,
Length,
j,
i;
tblRoot = tblCur;
for (j = strKeys.length - 1; j >= 0; j -= 1) {
str_key = strKeys[j];
Length = str_key.length;
for (i = 0; i < Length; i += 1) {
key = str_key.charAt(i);
if (tblCur.hasOwnProperty(key)) {
//生成子节点
tblCur = tblCur[key];
} else {
tblCur = tblCur[key] = {};
}
}
tblCur.end = true; //最后一个关键字没有分割符
tblCur = tblRoot;
}
return tblRoot;
},
search: function(content, tblRoot) {
'use strict';
var tblCur,
p_star = 0,
n = content.length,
p_end,
match, //是否找到匹配
match_key,
match_str,
arrMatch = [], //存储结果
arrLength = 0; //arrMatch的长度索引
while (p_star < n) {
tblCur = tblRoot; //回溯至根部
p_end = p_star;
match_str = '';
match = false;
do {
match_key = content.charAt(p_end);
if (!(tblCur = tblCur[match_key])) {
//本次匹配结束
p_star += 1;
break;
} else {
match_str += match_key;
}
p_end += 1;
if (tblCur.end === true) {
//是否匹配到尾部 //找到匹配关键字
match = true;
}
} while (true);
if (match === true) {
//最大匹配
arrMatch[arrLength] = {
//增强可读性
key: match_str,
begin: p_star - 1,
end: p_end
};
arrLength += 1;
p_star = p_end;
}
}
return arrMatch;
}
};
测试代码：
function test(strContent, strKeys) {
var arrMatch,
tblRoot = treeSearch.makeTree(strKeys),
t = new Date();
arrMatch = treeSearch.search(strContent, tblRoot);
console.log('time is: ' + (new Date() - t) + 'mm');
console.log(arrMatch);
}
var s = (function() {
var Things = [' ', '\n', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
var s = '';
for (var i = 1000000; i >= 0; i--) {
s += Things[parseInt(Math.random() * Things.length) % Things.length];
}
return s;
})();
test(s, ['abc', 'efge', 'fun', 'tree']);