Max Difference You Can Get From Changing an Integer LeetCode solution in C++

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class Solution {
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 public:
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  int power10(int n) {
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    int total = 1;
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    for (int i = 0; i < n; i++) {
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      total *= 10;
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    }
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    return total;
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  }
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  int maxDiff(int num) {
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    vector<int> v;
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    vector<int> w;
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    int n = num;
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    while (n > 0) {
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      v.push_back(n % 10);
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      w.push_back(n % 10);
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      n /= 10;
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    }
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    // Finding maximum number
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    int d = v.size();
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    int j = d - 1;
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    for (int i = d - 1; i >= 0; i--) {
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      if (v[i] != 9) {
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        j = i;
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        break;
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      }
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    }
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    for (int i = 0; i <= j; i++) {
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      if (v[i] == v[j]) {
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        v[i] = 9;
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      }
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    }
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    long long int res = 0;
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    for (int i = d - 1; i >= 0; i--) {
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      res += (v[i] * power10(i));
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    }
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    // Finding minimum number
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    int t = w.size();
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    if (w[t - 1] == 1) {
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      int l = -1;
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      for (int i = t - 2; i >= 0; i--) {
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        if (w[i] != 0 && w[i] != 1) {
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          l = i;
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          break;
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        }
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      }
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      for (int i = 0; i <= l; i++) {
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        if (w[i] == w[l]) {
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          w[i] = 0;
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        }
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      }
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    } else {
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      for (int i = 0; i < t; i++) {
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        if (w[i] == w[t - 1]) {
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          w[i] = 1;
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        }
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      }
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    }
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    long long int res2 = 0;
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    for (int i = t - 1; i >= 0; i--) {
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      res2 += (power10(i) * w[i]);
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    }
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    return res - res2;
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  }
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};