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// 402. Remove K Digits
#include "leetcode.h"
/*
* given string 'num' representing a non-negative integer 'num', and an integer
* 'k' return the smallest possible integer after removing 'k' digits from
* 'num'.
*/
char *removeKdigits(char *num, int k) {
int n = strlen(num), s_idx = 1;
if (k >= n)
return "0";
int *stk = malloc(n * sizeof(int));
stk[0] = 0;
for (int i = 1; i < n; i++) {
if (!k) {
stk[s_idx] = i;
s_idx++;
continue;
}
while (s_idx && num[i] < num[stk[s_idx - 1]]) {
s_idx--, k--;
if (!k)
break;
}
stk[s_idx] = i;
s_idx++;
}
int i = 0, a_idx = 0;
s_idx -= k;
char *ans = malloc(s_idx + 1);
for (i = 0; i < s_idx; i++)
if (num[stk[i]] != '0')
break;
for (int j = i; j < s_idx; j++) {
ans[a_idx] = num[stk[j]];
a_idx++;
}
ans[a_idx] = '\0';
if (!a_idx)
return "0";
return ans;
}
int main() {
char *n1 = "1432219", *n2 = "10200", *n3 = "10";
printf("%s\n", removeKdigits(n1, 3)); // expect: 1219
printf("%s\n", removeKdigits(n2, 1)); // expect: 200
printf("%s\n", removeKdigits(n3, 2)); // expect: 0
}
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