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

Data structure and algorithm of TypeScript

export function lcstr(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);
    }
    let maxCol = 0, maxRow = 0, longestLength = 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;
            }
            if (arr[i][j] > longestLength) {
                longestLength = arr[i][j];
                maxRow = i;
                maxCol = j;
            }
        }
    }
    const subArr = [];
    while (arr[maxRow][maxCol] > 0) {
        subArr.unshift(text1[maxRow - 1]);
        maxRow--;
        maxCol--;
    }
    return subArr.join("");
}
export function lcstropt(text1, text2) {
    if (!text1 || !text2) {
        return "";
    }
    const length1 = text1.length;
    const length2 = text2.length;
    const arr = new Array(length2 + 1).fill(0);
    const topArr = new Array(length2 + 1).fill(0);
    let maxCol = 0, longestLength = 0;
    for (let i = 1; i <= length1; i++) {
        for (let j = 1; j <= length2; j++) {
            if (text1[i - 1] === text2[j - 1]) {
                arr[j] = topArr[j - 1] + 1;
            }
            else {
                arr[j] = 0;
            }
            if (arr[j] > longestLength) {
                longestLength = arr[j];
                maxCol = j;
            }
        }
        for (let k = 0; k < arr.length; k++) {
            topArr[k] = arr[k];
        }
    }
    const subArr = [];
    while (longestLength > 0) {
        subArr.unshift(text2[maxCol - 1]);
        maxCol--;
        longestLength--;
    }
    return subArr.join("");
}