1143-最长公共子序列

动态规划处理，效率不高，还有优化空间

/**
 * @param {string} text1
 * @param {string} text2
 * @return {number}
 */
var longestCommonSubsequence = function(text1, text2) {
  const arr1 = text1.split('');
  const arr2 = text2.split('');
  arr1.unshift('');
  arr2.unshift('');
  let _arr = [];
  for (let i = 0; i < arr1.length; i++) {
    _arr[i] = [];
    for (let j = 0; j < arr2.length; j++) {
      if (arr1[i] === '' || arr2[j] === '') {
        _arr[i][j] = 0;
        continue;
      }
      if (arr1[i] === arr2[j]) {
        _arr[i][j] = _arr[i-1][j-1] + 1;
      } else {
        _arr[i][j] = Math.max(_arr[i][j-1], _arr[i-1][j]);
      }
    }
  }
  return _arr[arr1.length - 1][arr2.length - 1];
};