ts-ds-tool/resource/algorithms/lcs/lcs.js

Data structure and algorithm of TypeScript

export function lcs(text1, text2) {
    if (!text1 || !text2) {
        return "";
    }
    const length1 = text1.length;
    const length2 = text2.length;
    const arr = new Array(length1 + 1);
    for (let index = 0; index <= length1; index++) {
        arr[index] = new Array(length2 + 1).fill(0);
    }
    for (let i = 1; i <= length1; i++) {
        for (let j = 1; j <= length2; j++) {
            if (text1[i - 1] === text2[j - 1]) {
                arr[i][j] = arr[i - 1][j - 1] + 1;
            }
            else {
                arr[i][j] = Math.max(arr[i][j - 1], arr[i - 1][j]);
            }
        }
    }
    if (!arr[length1][length2]) {
        return "";
    }
    let i = length1, j = length2;
    const columnArr = [];
    while (i > 0 && j > 0) {
        if (text1[i - 1] === text2[j - 1]) {
            columnArr.unshift(text1[i - 1]);
            i--;
            j--;
        }
        else if (arr[i][j] === arr[i][j - 1]) {
            j--;
        }
        else {
            i--;
        }
    }
    return columnArr.join("");
}