Commit589ac08

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decode.

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	`1`	`+packageAlgorithms.dp;`
	`2`	`+`
	`3`	`+publicclassNumDecodings {`
	`4`	`+publicintnumDecodings(Strings) {`
	`5`	`+if (s ==null \|\|s.length() ==0) {`
	`6`	`+return0;`
	`7`	`+ }`
	`8`	`+`
	`9`	`+intlen =s.length();`
	`10`	`+`
	`11`	`+// D[i] 表示含有i个字符的子串的DECODE WAYS.`
	`12`	`+int[]D =newint[len +1];`
	`13`	`+`
	`14`	`+D[0] =1;`
	`15`	`+`
	`16`	`+for (inti =1;i <=len;i++) {`
	`17`	`+D[i] =0;`
	`18`	`+`
	`19`	`+// 现在正在考察的字符的索引.`
	`20`	`+intindex =i -1;`
	`21`	`+// 最后一个字符独立解码`
	`22`	`+if (isValidSingle(s.charAt(index))) {`
	`23`	`+D[i] +=D[i -1];`
	`24`	`+ }`
	`25`	`+`
	`26`	`+// 最后一个字符与上一个字符一起解码`
	`27`	`+if (i >1 &&isValidTwo(s.substring(index -1,index +1))) {`
	`28`	`+D[i] +=D[i -2];`
	`29`	`+ }`
	`30`	`+ }`
	`31`	`+`
	`32`	`+returnD[len];`
	`33`	`+ }`
	`34`	`+`
	`35`	`+publicbooleanisValidSingle(charc) {`
	`36`	`+if (c >='1' &&c <='9') {`
	`37`	`+returntrue;`
	`38`	`+ }`
	`39`	`+`
	`40`	`+returnfalse;`
	`41`	`+ }`
	`42`	`+`
	`43`	`+publicbooleanisValidTwo(Strings) {`
	`44`	`+intnum =Integer.parseInt(s);`
	`45`	`+`
	`46`	`+return (num >=10 &&num <=26);`
	`47`	`+ }`
	`48`	`+}`

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