早上开车等红绿灯时想到几个月前写的一个算法，应该可以更简单，今天重新写了一遍
寻找下一个数字，例如输入345，输出354
思路：从最右边位和上一位对比，如果大，就往前移，移动完，尾数排序，从小到大，保证次大
代码
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| //字符串分成数组
NSMutableArray *convertStringToArray(NSString *str){
NSMutableArray *marr = [NSMutableArray array];
for (NSInteger i = 0; i < str.length; i++) {
[marr addObject:[str substringWithRange:NSMakeRange(i, 1)]];
}
return marr;
}
//数组拼成字符串
NSString *convertArrayToString(NSArray *arr){
NSMutableString *mstr = [NSMutableString string];
for (NSString *str in arr) {
[mstr appendString:str];
}
return mstr;
}
//冒泡排序 从小到大
NSString *bubbleSort(NSString *str){
NSArray *sortedArray = convertStringToArray(str);
NSMutableArray *marr = [NSMutableArray arrayWithArray:sortedArray];
//最后一位的索引
unsigned long j = marr.count-1;
for (;j>0;j--) {
BOOL didSort = NO;
//第一轮结束
for (int i=0; i<j; i++) {
NSString *pre = marr[i];
NSString *next = marr[i+1];
if (pre.integerValue > next.integerValue) {
[marr exchangeObjectAtIndex:i+1 withObjectAtIndex:i];
didSort = YES;
}
}
if (!didSort) {
break;
}
}
NSMutableString *mstr = [NSMutableString string];
for (NSString *str in marr) {
[mstr appendString:str];
}
return mstr;
}
NSString *findNextLargerNum(NSString *oriNum){
NSString *resultStr = oriNum;
NSMutableArray *oriNumMArr =[NSMutableArray arrayWithArray:convertStringToArray(oriNum)];
for (int j = oriNumMArr.count-1; j>0; j--) {
BOOL getResult = NO;
NSString *last = oriNumMArr[j];
for (int i = j-1; i>=0; i--) {
NSString *pre = oriNumMArr[i];
if (last.integerValue > pre.integerValue) {
[oriNumMArr exchangeObjectAtIndex:i withObjectAtIndex:j];
NSRange range = NSMakeRange(i+1, oriNumMArr.count - 1 - i);
NSString *surfixStr = convertArrayToString([oriNumMArr subarrayWithRange:range]);
NSString *surResultStr = bubbleSort(surfixStr);
NSString *preStr = convertArrayToString([oriNumMArr subarrayWithRange:NSMakeRange(0,i+1)]);
resultStr = [NSString stringWithFormat:@"%@%@",preStr,surResultStr];
getResult = YES;
break;
}
}
if (getResult) {
break;
}
}
return resultStr;
}
|
使用：
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| NSString *str = findNextLargerNum(@"8976");
NSLog(@"======%@",str);
//打印结果
======9678
|