如何解决indexOfString str-等于其他字符串
我需要编写一种方法来检查其他字符串上的\“ String str \”，并返回str开始的索引。 听起来像是家庭作业，是一些家庭作业，但供我学习测试用... 我试过了：public int IndexOf (String str) {
for (i= 0;i<_st.length();i++)
{
if (_st.charAt(i) == str.charAt(i)) {
i++;
if (_st.charAt(i) == str.charAt(i)) {
return i;
}
}
}
return -1;
}
解决方法
恐怕你还不亲密。
这是您要做的：
循环处理字符串的字符（您应该在该字符上执行
indexOf
Loop master string
for every character (using index i,lets say)
check whether this is same as first character of the other string
if it is
//potential match
loop through the characters in the child string (lets say using index j)
match them with the consecutive characters in the master string
(something like master[j+i] == sub[j])
If everything match,\'i\' is what you want
otherwise,continue with the master,hoping you find a match
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/**
* Returns the index within this string of the first occurrence of the
* specified substring. The integer returned is the smallest value
* <i>k</i> such that:
* <blockquote><pre>
* this.startsWith(str,<i>k</i>)
* </pre></blockquote>
* is <code>true</code>.
*
* @param str any string.
* @return if the string argument occurs as a substring within this
* object,then the index of the first character of the first
* such substring is returned; if it does not occur as a
* substring,<code>-1</code> is returned.
*/
public int indexOf(String str) {
return indexOf(str,0);
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring,starting at the specified index. The integer
* returned is the smallest value <tt>k</tt> for which:
* <blockquote><pre>
* k >= Math.min(fromIndex,this.length()) && this.startsWith(str,k)
* </pre></blockquote>
* If no such value of <i>k</i> exists,then -1 is returned.
*
* @param str the substring for which to search.
* @param fromIndex the index from which to start the search.
* @return the index within this string of the first occurrence of the
* specified substring,starting at the specified index.
*/
public int indexOf(String str,int fromIndex) {
return indexOf(value,offset,count,str.value,str.offset,str.count,fromIndex);
}
/**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched,and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int indexOf(char[] source,int sourceOffset,int sourceCount,char[] target,int targetOffset,int targetCount,int fromIndex) {
if (fromIndex >= sourceCount) {
return (targetCount == 0 ? sourceCount : -1);
}
if (fromIndex < 0) {
fromIndex = 0;
}
if (targetCount == 0) {
return fromIndex;
}
char first = target[targetOffset];
int max = sourceOffset + (sourceCount - targetCount);
for (int i = sourceOffset + fromIndex; i <= max; i++) {
/* Look for first character. */
if (source[i] != first) {
while (++i <= max && source[i] != first);
}
/* Found first character,now look at the rest of v2 */
if (i <= max) {
int j = i + 1;
int end = j + targetCount - 1;
for (int k = targetOffset + 1; j < end && source[j] ==
target[k]; j++,k++);
if (j == end) {
/* Found whole string. */
return i - sourceOffset;
}
}
}
return -1;
}
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