php 数字字符串相加,php 数字字符串 +1 操作 累加 加一 (不溢出)

* inc.php

function inc($s) {

if (empty($s)) {return "1";}

if ( ! isset($s[1]) ) {

$code = ord($s[0]) + 1;

if ($code <= ord("9")) {

return chr($code);

}

return "10";

}

$n = strlen($s);

$code = ord($s[$n-1]) +1;

if ($code <= ord("9")) {

return substr($s, 0, $n-1).chr($code);

}

return inc(substr($s, 0, $n-1))."0";

}

$s = "2147483647";

$n = 10000;

while ($n-- > 0) {

// printf("%s\n", $s);

$s = inc($s);

}

printf("%s\n", $s); // "2147493647"

递归，如果需要进位, 先计算除去最后一个字符的字符串, 最后一个字符置为'0'; 单个数字字符0-9显然好处理。

* test:

$m = 2147483647;

$n = 10000;

while ($n-- > 0) {

// printf("%d\n", $m);

$m++;

}

printf("%d\n", $m);

比较结果一致

* add2.php  // 遍历1-4位大写字母

function add($s) {

if (empty($s)) {return "A";}

if ( ! isset($s[1]) ) {

$code = ord($s[0]) + 1;

if ($code <= ord("Z")) {

return chr($code);

}

return "AA";

}

$n = strlen($s);

$code = ord($s[$n-1]) +1;

if ($code <= ord("Z")) {

return substr($s, 0, $n-1).chr($code);

}

return add(substr($s, 0, $n-1))."A";

}

$s = "";

do {

$s = add($s);

printf("%s\n", $s);

} while ($s != "ZZZZ");