113 lines
2.4 KiB
TypeScript
113 lines
2.4 KiB
TypeScript
/**
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* Levenshtein 距离算法
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* 用于计算两个字符串之间的编辑距离
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*/
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/**
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* 内部最小值计算函数
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*/
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function _min(d0: number, d1: number, d2: number, bx: number, ay: number): number {
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return d0 < d1 || d2 < d1
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? d0 > d2
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? d2 + 1
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: d0 + 1
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: bx === ay
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? d1
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: d1 + 1;
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}
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/**
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* 计算两个字符串之间的 Levenshtein 距离
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* @param a 第一个字符串
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* @param b 第二个字符串
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* @returns 编辑距离
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*/
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export function levenshteinDistance(a: string, b: string): number {
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if (a === b) {
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return 0;
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}
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if (a.length > b.length) {
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const tmp = a;
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a = b;
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b = tmp;
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}
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let la = a.length;
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let lb = b.length;
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while (la > 0 && (a.charCodeAt(la - 1) === b.charCodeAt(lb - 1))) {
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la--;
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lb--;
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}
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let offset = 0;
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while (offset < la && (a.charCodeAt(offset) === b.charCodeAt(offset))) {
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offset++;
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}
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la -= offset;
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lb -= offset;
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if (la === 0 || lb < 3) {
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return lb;
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}
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let x = 0;
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let y: number;
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let d0: number;
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let d1: number;
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let d2: number;
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let d3: number;
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let dd = 0;
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let dy: number;
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let ay: number;
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let bx0: number;
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let bx1: number;
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let bx2: number;
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let bx3: number;
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const vector: number[] = [];
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for (y = 0; y < la; y++) {
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vector.push(y + 1);
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vector.push(a.charCodeAt(offset + y));
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}
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const len = vector.length - 1;
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for (; x < lb - 3;) {
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bx0 = b.charCodeAt(offset + (d0 = x));
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bx1 = b.charCodeAt(offset + (d1 = x + 1));
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bx2 = b.charCodeAt(offset + (d2 = x + 2));
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bx3 = b.charCodeAt(offset + (d3 = x + 3));
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x += 4;
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dd = x;
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for (y = 0; y < len; y += 2) {
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dy = vector[y];
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ay = vector[y + 1];
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d0 = _min(dy, d0, d1, bx0, ay);
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d1 = _min(d0, d1, d2, bx1, ay);
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d2 = _min(d1, d2, d3, bx2, ay);
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dd = _min(d2, d3, dd, bx3, ay);
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vector[y] = dd;
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d3 = d2;
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d2 = d1;
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d1 = d0;
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d0 = dy;
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}
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}
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for (; x < lb;) {
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bx0 = b.charCodeAt(offset + (d0 = x));
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dd = ++x;
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for (y = 0; y < len; y += 2) {
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dy = vector[y];
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vector[y] = dd = _min(dy, d0, dd, bx0, vector[y + 1]);
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d0 = dy;
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}
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}
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return dd;
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}
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