js 动态规划算法:DNA序列比对

　　JavaScript动态序列比对代码，随便 写着玩的，在网上见到用VC、VB写的比较多，这个算法以前在高中课本上见到过，我只是用Js写一下试试，或许还不是太准确。

<script> function pairaln(seq1, seq2){ // scoring scheme var MATCH = 1; // +1 for letters that match var MISMATCH = -1; // -1 for letters that mismatch var GAP = -1; // -1 for any gap // initialization var score=[[]]; var pointer=[[]]; score[0][0] = 0; pointer[0][0] = 0; var l1=seq1.length var l2=seq2.length for(var j = 1; j <= l1; j++) { score[0][j] = GAP * j; pointer[0][j] = 2; } for (var i = 1; i <= l2; i++) { score[i]=[]; pointer[i]=[]; score[i][0] = GAP * i; pointer[i][0] = 3; } // fill for(var i = 1; i <= l2; i++) { var letter2 = seq2.charAt(i-1); for(var j = 1; j <= l1; j++) { var diagonal_score, left_score, up_score; // calculate match score var letter1 = seq1.charAt(j-1); if (letter1 == letter2) { diagonal_score = score[i-1][j-1] + MATCH; } else { diagonal_score = score[i-1][j-1] + MISMATCH; } // calculate gap scores up_score = score[i-1][j] + GAP; left_score = score[i][j-1] + GAP; // choose best score if (diagonal_score >= up_score) { if (diagonal_score >= left_score) { score[i][j] = diagonal_score; pointer[i][j] = 1; } else { score[i][j] = left_score; pointer[i][j] = 2; } } else { if (up_score >= left_score) { score[i][j] = up_score; pointer[i][j] = 3; } else { score[i][j] = left_score; pointer[i][j] = 2; } } } } // trace-back var align1 = []; var align2 = []; // start at last cell of matrix var j = l1; var i = l2; while (1) { if(pointer[i][j] == 0)break // ends at first cell of matrix if (pointer[i][j] == 1) { align1[align1.length] = seq1.charAt(j-1); align2[align2.length] = seq2.charAt(i-1); i--; j--; } if (pointer[i][j] == 2) { align1[align1.length] = seq1.charAt(j-1); align2[align2.length] = "-"; j--; } if (pointer[i][j] == 3) { align1[align1.length] = "-"; align2[align2.length] = seq2.charAt(i-1); i--; } } align1 = align1.reverse(); align2 = align2.reverse(); return "序列：<p>"+seq1+"<br>"+seq2+"<p>比对结果：<table><tr><td>"+align1.join("</td><td>")+"</td></tr><tr><td>"+align2.join("</td><td>")+"</tr></table>" } document.write(pairaln('CTGGGCTGACTGA', 'GACTAGCTAGACTGA')) </script><br /><center>如不能显示效果，请按Ctrl+F5刷新本页，更多网页代码：<a href='http://www.veryhuo.com/' target='_blank'>http://www.veryhuo.com/</a></center>
提示：可修改后代码再运行!

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