标签：style io os ar for sp div on art
#!/usr/bin/env python
#encoding=gbkimport sys"""1. Set n to be the length of s. Set m to be the length of t. If n = 0, return m and exit. If m = 0, return n and exit.2. Construct a matrix containing 0..m rows and 0..n columns. Initialize the first row to 0..n. Initialize the first column to 0..m.3. Examine each character of s (i from 1 to n).4. Examine each character of t (j from 1 to m).5. If s[i] equals t[j], the cost is 0. If s[i] doesn‘t equal t[j], the cost is 1.6. Set cell d[i,j] of the matrix equal to the minimum of: a. The cell immediately above plus 1: d[i-1,j] + 1. b. The cell immediately to the left plus 1: d[i,j-1] + 1. c. The cell diagonally above and to the left plus the cost: d[i-1,j-1] + cost.After the iteration steps (3, 4, 5, 6) are complete, the distance is found in cell d[n,m]."""def show(matirx): for ir in range(0,len(matirx)): cl = matirx[ir] for il in range(0,len(cl)): print "%d "%matirx[ir][il], print "" print ""def minimum(a, b, c): mi = a if (b < mi): mi = b if (c < mi): mi = c return midef BLD(t, p): ut = unicode(t, "gbk") up = unicode(p, "gbk") m = len(ut) n = len(up) if m == 0:return " ".join("*" * len(up)), " ".join(up.encode("gbk")), " ".join("I"*len(up)) if n == 0:return " ".join(ut.encode("gbk")), " ".join("*" * len(ut)), " ".join("D"*len(ut)) d = [[0] * (m + 1)for i in range(0, n + 1)] b = [[0] * (m + 1)for i in range(0, n + 1)] #show(d) #show(b) for i in range(1, len(d[0])):d[0][i] = i for i in range(1, len(d)):d[i][0] = i #show(d) for i in range(1, len(d)):#row num, p‘s length for j in range(1, len(d[0])):#column num, t‘s length """ins cost:d[i - 1][j] + 1; del cost:d[i][j - 1] + 1; sub cost:d[i - 1][j - 1] + 0 if up[i - 1] == ut[j - 1] else 1""" d[i][j] = minimum(d[i - 1][j] + 1, d[i][j - 1] + 1, d[i - 1][j - 1]+ (0 if up[i - 1] == ut[j - 1] else 1)) """backtrace matrix:[1:tag ins | 2:tag del | 3:tag sub]""" if d[i][j] == d[i - 1][j] + 1: b[i][j] = 1 elif d[i][j] == d[i][j - 1] + 1: b[i][j] = 2 elif d[i][j] == d[i - 1][j - 1] + 0 if up[i - 1] == ut[j - 1] else 1: b[i][j] = 3 show(d) show(b) #print "t: %s\np: %s\ncost: %d"%(ut,up,d[n][m]) """put the best path point into a list""" bestPath = [] i = len(d) - 1 #row num j = len(d[0]) - 1 #column num while i != 0 or j != 0: bestPath.append([i, j, b[i][j]]) """ if tag is sub : i - 1, j - 1; b[i - 1][j - 1] if tag is del : j - 1 ; b[i][j - 1] if tag is ins : i - 1 ; b[i - 1][j] """ if b[i][j] == 1: i -= 1 elif b[i][j] == 2: j -= 1 elif b[i][j] == 3: i -= 1; j -= 1 else: if i > 0: i -= 1 if j > 0: j -=1 print bestPath """ read best path and print info part I: handle best path‘s first point part II: handle best path‘s left points """ it = "*" if bestPath[-1][1] == 0 else ut[bestPath[-1][1] - 1].encode("gbk") ip = "*" if bestPath[-1][0] == 0 else up[bestPath[-1][0] - 1].encode("gbk") sf = "" if bestPath[-1][2] == 1: sf = "I" elif bestPath[-1][2] == 2: sf = "D" elif bestPath[-1][2] == 3: sf = " " if ut[0] == up[0] else "S" else: sf = "I" if bestPath[-1][1] == 0 else "D" for i in range(len(bestPath) - 1, 0, -1): current = bestPath[i - 1] forward = bestPath[i] ip += up[current[0] - 1].encode("gbk") if current[0] != forward[0] and current[0] > 0 else "*" it += ut[current[1] - 1].encode("gbk") if current[1] != forward[1] and current[1] > 0 else "*" if current[2] == 1: sf += "I" elif current[2] == 2: sf += "D" elif current[2] == 3: sf += "S" if up[current[0] - 1] != ut[current[1] - 1] else " " else: sf += "I" if current[1] == 0 else "D" return " ".join(it), " ".join(ip), " ".join(sf)t = "abcdfx"p = "fdsxdf"st,sp,sf = BLD(t, p)print "\n%s\n%s\n%s"%(st, sp, sf)"""time cost: O(m * n)space cost: O(m * n)backtrace cost: O(m + n)"""标签：style io os ar for sp div on art
原文地址：http://www.cnblogs.com/ariesblogs/p/4046616.html
