Minimum Time to Make Rope Colorful LeetCode solution in Java

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class Solution {
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  public int minCost(String colors, int[] neededTime) {
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    return minCost(colors, neededTime, 0, neededTime.length - 1);
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  }
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  public int minCost(String colors, int[] neededTime, int start, int end) {
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    if (start == end) {
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      return 0;
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    }
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    int mid = (start + end) / 2;
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    int lEnd = mid;
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    int rStart = mid + 1;
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    int t1 = minCost(colors, neededTime, start, lEnd);
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    int t2 = minCost(colors, neededTime, rStart, end);
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    while (neededTime[lEnd] < 0 && lEnd >= start) {
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      --lEnd;
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    }
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    while (neededTime[rStart] < 0 && rStart <= end) {
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      ++rStart;
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    }
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    if (colors.charAt(lEnd) != colors.charAt(rStart)) {
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      return t1 + t2;
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    }
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    int removeTime = 0;
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    if (neededTime[lEnd] <= neededTime[rStart]) {
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      removeTime = neededTime[lEnd];
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      neededTime[lEnd] *= -1;
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    } else {
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      removeTime = neededTime[rStart];
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      neededTime[rStart] *= -1;
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    }
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    return t1 + t2 + removeTime;
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  }
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}